diff --git a/backend/app/api/deps.py b/backend/app/api/deps.py
index 5bef1169aa7..74103ae6134 100644
--- a/backend/app/api/deps.py
+++ b/backend/app/api/deps.py
@@ -17,7 +17,7 @@
 )
 
 
-def get_db() -> Generator:
+def get_db() -> Generator[Session, None, None]:
     with Session(engine) as session:
         yield session
 
diff --git a/backend/app/api/routes/users.py b/backend/app/api/routes/users.py
index 19865908fc7..661525e3fc4 100644
--- a/backend/app/api/routes/users.py
+++ b/backend/app/api/routes/users.py
@@ -1,7 +1,7 @@
 from typing import Any
 
 from fastapi import APIRouter, Depends, HTTPException
-from sqlmodel import delete, func, select
+from sqlmodel import col, delete, func, select
 
 from app import crud
 from app.api.deps import (
@@ -189,16 +189,17 @@ def delete_user(
     user = session.get(User, user_id)
     if not user:
         raise HTTPException(status_code=404, detail="User not found")
-
-    if (user == current_user and not current_user.is_superuser) or (
-        user != current_user and current_user.is_superuser
-    ):
-        statement = delete(Item).where(Item.owner_id == user_id)
-        session.exec(statement)
-        session.delete(user)
-        session.commit()
-        return Message(message="User deleted successfully")
+    elif user != current_user and not current_user.is_superuser:
+        raise HTTPException(
+            status_code=403, detail="The user doesn't have enough privileges"
+        )
     elif user == current_user and current_user.is_superuser:
         raise HTTPException(
             status_code=403, detail="Super users are not allowed to delete themselves"
         )
+
+    statement = delete(Item).where(col(Item.owner_id) == user_id)
+    session.exec(statement)  # type: ignore
+    session.delete(user)
+    session.commit()
+    return Message(message="User deleted successfully")
diff --git a/backend/app/core/config.py b/backend/app/core/config.py
index 8aeb7eef2a7..a9803c048c4 100644
--- a/backend/app/core/config.py
+++ b/backend/app/core/config.py
@@ -68,7 +68,7 @@ def assemble_db_connection(cls, v: str | None, info: ValidationInfo) -> Any:
     @field_validator("EMAILS_FROM_NAME")
     def get_project_name(cls, v: str | None, info: ValidationInfo) -> str:
         if not v:
-            return info.data["PROJECT_NAME"]
+            return str(info.data["PROJECT_NAME"])
         return v
 
     EMAIL_RESET_TOKEN_EXPIRE_HOURS: int = 48
@@ -89,7 +89,7 @@ def get_emails_enabled(cls, v: bool, info: ValidationInfo) -> bool:
     FIRST_SUPERUSER: str
     FIRST_SUPERUSER_PASSWORD: str
     USERS_OPEN_REGISTRATION: bool = False
-    model_config = SettingsConfigDict(case_sensitive=True)
+    model_config = SettingsConfigDict(env_file=".env")
 
 
-settings = Settings()
+settings = Settings()  # type: ignore
diff --git a/backend/app/core/security.py b/backend/app/core/security.py
index c9e5085f087..217bb8d43e4 100644
--- a/backend/app/core/security.py
+++ b/backend/app/core/security.py
@@ -12,13 +12,8 @@
 ALGORITHM = "HS256"
 
 
-def create_access_token(subject: str | Any, expires_delta: timedelta = None) -> str:
-    if expires_delta:
-        expire = datetime.utcnow() + expires_delta
-    else:
-        expire = datetime.utcnow() + timedelta(
-            minutes=settings.ACCESS_TOKEN_EXPIRE_MINUTES
-        )
+def create_access_token(subject: str | Any, expires_delta: timedelta) -> str:
+    expire = datetime.utcnow() + expires_delta
     to_encode = {"exp": expire, "sub": str(subject)}
     encoded_jwt = jwt.encode(to_encode, settings.SECRET_KEY, algorithm=ALGORITHM)
     return encoded_jwt
diff --git a/backend/app/main.py b/backend/app/main.py
index e68508b2251..849b545ef23 100644
--- a/backend/app/main.py
+++ b/backend/app/main.py
@@ -6,7 +6,7 @@
 from app.core.config import settings
 
 
-def custom_generate_unique_id(route: APIRoute):
+def custom_generate_unique_id(route: APIRoute) -> str:
     return f"{route.tags[0]}-{route.name}"
 
 
diff --git a/backend/app/models.py b/backend/app/models.py
index 10091303dc7..6b506502d38 100644
--- a/backend/app/models.py
+++ b/backend/app/models.py
@@ -25,7 +25,7 @@ class UserCreateOpen(SQLModel):
 # Properties to receive via API on update, all are optional
 # TODO replace email str with EmailStr when sqlmodel supports it
 class UserUpdate(UserBase):
-    email: str | None = None
+    email: str | None = None  # type: ignore
     password: str | None = None
 
 
@@ -70,7 +70,7 @@ class ItemCreate(ItemBase):
 
 # Properties to receive on item update
 class ItemUpdate(ItemBase):
-    title: str | None = None
+    title: str | None = None  # type: ignore
 
 
 # Database model, database table inferred from class name
diff --git a/backend/app/tests/api/api_v1/test_items.py b/backend/app/tests/api/api_v1/test_items.py
index 20eca1e575b..56cfa95c4f7 100644
--- a/backend/app/tests/api/api_v1/test_items.py
+++ b/backend/app/tests/api/api_v1/test_items.py
@@ -6,7 +6,7 @@
 
 
 def test_create_item(
-    client: TestClient, superuser_token_headers: dict, db: Session
+    client: TestClient, superuser_token_headers: dict[str, str], db: Session
 ) -> None:
     data = {"title": "Foo", "description": "Fighters"}
     response = client.post(
@@ -23,7 +23,7 @@ def test_create_item(
 
 
 def test_read_item(
-    client: TestClient, superuser_token_headers: dict, db: Session
+    client: TestClient, superuser_token_headers: dict[str, str], db: Session
 ) -> None:
     item = create_random_item(db)
     response = client.get(
@@ -39,7 +39,7 @@ def test_read_item(
 
 
 def test_read_item_not_found(
-    client: TestClient, superuser_token_headers: dict, db: Session
+    client: TestClient, superuser_token_headers: dict[str, str], db: Session
 ) -> None:
     response = client.get(
         f"{settings.API_V1_STR}/items/999",
@@ -51,7 +51,7 @@ def test_read_item_not_found(
 
 
 def test_read_item_not_enough_permissions(
-    client: TestClient, normal_user_token_headers: dict, db: Session
+    client: TestClient, normal_user_token_headers: dict[str, str], db: Session
 ) -> None:
     item = create_random_item(db)
     response = client.get(
@@ -64,7 +64,7 @@ def test_read_item_not_enough_permissions(
 
 
 def test_read_items(
-    client: TestClient, superuser_token_headers: dict, db: Session
+    client: TestClient, superuser_token_headers: dict[str, str], db: Session
 ) -> None:
     create_random_item(db)
     create_random_item(db)
@@ -78,7 +78,7 @@ def test_read_items(
 
 
 def test_update_item(
-    client: TestClient, superuser_token_headers: dict, db: Session
+    client: TestClient, superuser_token_headers: dict[str, str], db: Session
 ) -> None:
     item = create_random_item(db)
     data = {"title": "Updated title", "description": "Updated description"}
@@ -96,7 +96,7 @@ def test_update_item(
 
 
 def test_update_item_not_found(
-    client: TestClient, superuser_token_headers: dict, db: Session
+    client: TestClient, superuser_token_headers: dict[str, str], db: Session
 ) -> None:
     data = {"title": "Updated title", "description": "Updated description"}
     response = client.put(
@@ -110,7 +110,7 @@ def test_update_item_not_found(
 
 
 def test_update_item_not_enough_permissions(
-    client: TestClient, normal_user_token_headers: dict, db: Session
+    client: TestClient, normal_user_token_headers: dict[str, str], db: Session
 ) -> None:
     item = create_random_item(db)
     data = {"title": "Updated title", "description": "Updated description"}
@@ -125,7 +125,7 @@ def test_update_item_not_enough_permissions(
 
 
 def test_delete_item(
-    client: TestClient, superuser_token_headers: dict, db: Session
+    client: TestClient, superuser_token_headers: dict[str, str], db: Session
 ) -> None:
     item = create_random_item(db)
     response = client.delete(
@@ -138,7 +138,7 @@ def test_delete_item(
 
 
 def test_delete_item_not_found(
-    client: TestClient, superuser_token_headers: dict, db: Session
+    client: TestClient, superuser_token_headers: dict[str, str], db: Session
 ) -> None:
     response = client.delete(
         f"{settings.API_V1_STR}/items/999",
@@ -150,7 +150,7 @@ def test_delete_item_not_found(
 
 
 def test_delete_item_not_enough_permissions(
-    client: TestClient, normal_user_token_headers: dict, db: Session
+    client: TestClient, normal_user_token_headers: dict[str, str], db: Session
 ) -> None:
     item = create_random_item(db)
     response = client.delete(
diff --git a/backend/app/tests/api/api_v1/test_login.py b/backend/app/tests/api/api_v1/test_login.py
index 6102c68d61c..7b8231dc31a 100644
--- a/backend/app/tests/api/api_v1/test_login.py
+++ b/backend/app/tests/api/api_v1/test_login.py
@@ -1,7 +1,8 @@
-from app.utils import generate_password_reset_token
 from fastapi.testclient import TestClient
+from pytest_mock import MockerFixture
 
 from app.core.config import settings
+from app.utils import generate_password_reset_token
 
 
 def test_get_access_token(client: TestClient) -> None:
@@ -38,7 +39,7 @@ def test_use_access_token(
 
 
 def test_recovery_password(
-    client: TestClient, normal_user_token_headers: dict[str, str], mocker
+    client: TestClient, normal_user_token_headers: dict[str, str], mocker: MockerFixture
 ) -> None:
     mocker.patch("app.utils.send_email", return_value=None)
     mocker.patch("app.core.config.settings.EMAILS_ENABLED", True)
diff --git a/backend/app/tests/api/api_v1/test_users.py b/backend/app/tests/api/api_v1/test_users.py
index ae2138e578e..b09a2b37b7b 100644
--- a/backend/app/tests/api/api_v1/test_users.py
+++ b/backend/app/tests/api/api_v1/test_users.py
@@ -1,4 +1,5 @@
 from fastapi.testclient import TestClient
+from pytest_mock import MockerFixture
 from sqlmodel import Session
 
 from app import crud
@@ -30,7 +31,10 @@ def test_get_users_normal_user_me(
 
 
 def test_create_user_new_email(
-    client: TestClient, superuser_token_headers: dict, db: Session, mocker
+    client: TestClient,
+    superuser_token_headers: dict[str, str],
+    db: Session,
+    mocker: MockerFixture,
 ) -> None:
     mocker.patch("app.utils.send_email")
     mocker.patch("app.core.config.settings.EMAILS_ENABLED", True)
@@ -50,7 +54,7 @@ def test_create_user_new_email(
 
 
 def test_get_existing_user(
-    client: TestClient, superuser_token_headers: dict, db: Session
+    client: TestClient, superuser_token_headers: dict[str, str], db: Session
 ) -> None:
     username = random_email()
     password = random_lower_string()
@@ -107,7 +111,7 @@ def test_get_existing_user_permissions_error(
 
 
 def test_create_user_existing_username(
-    client: TestClient, superuser_token_headers: dict, db: Session
+    client: TestClient, superuser_token_headers: dict[str, str], db: Session
 ) -> None:
     username = random_email()
     # username = email
@@ -140,7 +144,7 @@ def test_create_user_by_normal_user(
 
 
 def test_retrieve_users(
-    client: TestClient, superuser_token_headers: dict, db: Session
+    client: TestClient, superuser_token_headers: dict[str, str], db: Session
 ) -> None:
     username = random_email()
     password = random_lower_string()
@@ -179,7 +183,7 @@ def test_update_user_me(
 
 
 def test_update_password_me(
-    client: TestClient, superuser_token_headers: dict, db: Session
+    client: TestClient, superuser_token_headers: dict[str, str], db: Session
 ) -> None:
     new_password = random_lower_string()
     data = {
@@ -209,7 +213,7 @@ def test_update_password_me(
 
 
 def test_update_password_me_incorrect_password(
-    client: TestClient, superuser_token_headers: dict, db: Session
+    client: TestClient, superuser_token_headers: dict[str, str], db: Session
 ) -> None:
     new_password = random_lower_string()
     data = {"current_password": new_password, "new_password": new_password}
@@ -224,7 +228,7 @@ def test_update_password_me_incorrect_password(
 
 
 def test_update_password_me_same_password_error(
-    client: TestClient, superuser_token_headers: dict, db: Session
+    client: TestClient, superuser_token_headers: dict[str, str], db: Session
 ) -> None:
     data = {
         "current_password": settings.FIRST_SUPERUSER_PASSWORD,
@@ -242,7 +246,7 @@ def test_update_password_me_same_password_error(
     )
 
 
-def test_create_user_open(client: TestClient, mocker) -> None:
+def test_create_user_open(client: TestClient, mocker: MockerFixture) -> None:
     mocker.patch("app.core.config.settings.USERS_OPEN_REGISTRATION", True)
     username = random_email()
     password = random_lower_string()
@@ -258,7 +262,9 @@ def test_create_user_open(client: TestClient, mocker) -> None:
     assert created_user["full_name"] == full_name
 
 
-def test_create_user_open_forbidden_error(client: TestClient, mocker) -> None:
+def test_create_user_open_forbidden_error(
+    client: TestClient, mocker: MockerFixture
+) -> None:
     mocker.patch("app.core.config.settings.USERS_OPEN_REGISTRATION", False)
     username = random_email()
     password = random_lower_string()
@@ -272,7 +278,9 @@ def test_create_user_open_forbidden_error(client: TestClient, mocker) -> None:
     assert r.json()["detail"] == "Open user registration is forbidden on this server"
 
 
-def test_create_user_open_already_exists_error(client: TestClient, mocker) -> None:
+def test_create_user_open_already_exists_error(
+    client: TestClient, mocker: MockerFixture
+) -> None:
     mocker.patch("app.core.config.settings.USERS_OPEN_REGISTRATION", True)
     password = random_lower_string()
     full_name = random_lower_string()
@@ -382,6 +390,7 @@ def test_delete_user_current_super_user_error(
     client: TestClient, superuser_token_headers: dict[str, str], db: Session
 ) -> None:
     super_user = crud.get_user_by_email(session=db, email=settings.FIRST_SUPERUSER)
+    assert super_user
     user_id = super_user.id
 
     r = client.delete(
diff --git a/backend/app/tests/conftest.py b/backend/app/tests/conftest.py
index 502a45049a3..90ab39a357f 100644
--- a/backend/app/tests/conftest.py
+++ b/backend/app/tests/conftest.py
@@ -13,7 +13,7 @@
 
 
 @pytest.fixture(scope="session", autouse=True)
-def db() -> Generator:
+def db() -> Generator[Session, None, None]:
     with Session(engine) as session:
         init_db(session)
         yield session
@@ -25,7 +25,7 @@ def db() -> Generator:
 
 
 @pytest.fixture(scope="module")
-def client() -> Generator:
+def client() -> Generator[TestClient, None, None]:
     with TestClient(app) as c:
         yield c
 
diff --git a/backend/app/tests/scripts/test_backend_pre_start.py b/backend/app/tests/scripts/test_backend_pre_start.py
index 29173f996e7..4d9ec388008 100644
--- a/backend/app/tests/scripts/test_backend_pre_start.py
+++ b/backend/app/tests/scripts/test_backend_pre_start.py
@@ -1,21 +1,22 @@
 from unittest.mock import MagicMock
 
+from pytest_mock import MockerFixture
 from sqlmodel import select
 
 from app.backend_pre_start import init, logger
 
 
-def test_init_successful_connection(mocker):
+def test_init_successful_connection(mocker: MockerFixture) -> None:
     engine_mock = MagicMock()
 
     session_mock = MagicMock()
     exec_mock = MagicMock(return_value=True)
-    session_mock.configure_mock(**{'exec.return_value': exec_mock})
-    mocker.patch('sqlmodel.Session', return_value=session_mock)
+    session_mock.configure_mock(**{"exec.return_value": exec_mock})
+    mocker.patch("sqlmodel.Session", return_value=session_mock)
 
-    mocker.patch.object(logger, 'info')
-    mocker.patch.object(logger, 'error')
-    mocker.patch.object(logger, 'warn')
+    mocker.patch.object(logger, "info")
+    mocker.patch.object(logger, "error")
+    mocker.patch.object(logger, "warn")
 
     try:
         init(engine_mock)
@@ -23,6 +24,10 @@ def test_init_successful_connection(mocker):
     except Exception:
         connection_successful = False
 
-    assert connection_successful, "The database connection should be successful and not raise an exception."
+    assert (
+        connection_successful
+    ), "The database connection should be successful and not raise an exception."
 
-    assert session_mock.exec.called_once_with(select(1)), "The session should execute a select statement once."
+    assert session_mock.exec.called_once_with(
+        select(1)
+    ), "The session should execute a select statement once."
diff --git a/backend/app/tests/scripts/test_celery_pre_start.py b/backend/app/tests/scripts/test_celery_pre_start.py
index 67c3f5cbe08..a557e0d2f0f 100644
--- a/backend/app/tests/scripts/test_celery_pre_start.py
+++ b/backend/app/tests/scripts/test_celery_pre_start.py
@@ -1,21 +1,22 @@
 from unittest.mock import MagicMock
 
+from pytest_mock import MockerFixture
 from sqlmodel import select
 
 from app.celeryworker_pre_start import init, logger
 
 
-def test_init_successful_connection(mocker):
+def test_init_successful_connection(mocker: MockerFixture) -> None:
     engine_mock = MagicMock()
 
     session_mock = MagicMock()
     exec_mock = MagicMock(return_value=True)
-    session_mock.configure_mock(**{'exec.return_value': exec_mock})
-    mocker.patch('sqlmodel.Session', return_value=session_mock)
+    session_mock.configure_mock(**{"exec.return_value": exec_mock})
+    mocker.patch("sqlmodel.Session", return_value=session_mock)
 
-    mocker.patch.object(logger, 'info')
-    mocker.patch.object(logger, 'error')
-    mocker.patch.object(logger, 'warn')
+    mocker.patch.object(logger, "info")
+    mocker.patch.object(logger, "error")
+    mocker.patch.object(logger, "warn")
 
     try:
         init(engine_mock)
@@ -23,6 +24,10 @@ def test_init_successful_connection(mocker):
     except Exception:
         connection_successful = False
 
-    assert connection_successful, "The database connection should be successful and not raise an exception."
+    assert (
+        connection_successful
+    ), "The database connection should be successful and not raise an exception."
 
-    assert session_mock.exec.called_once_with(select(1)), "The session should execute a select statement once."
+    assert session_mock.exec.called_once_with(
+        select(1)
+    ), "The session should execute a select statement once."
diff --git a/backend/app/tests/scripts/test_test_pre_start.py b/backend/app/tests/scripts/test_test_pre_start.py
index 485338d4e23..de5b61ab3a7 100644
--- a/backend/app/tests/scripts/test_test_pre_start.py
+++ b/backend/app/tests/scripts/test_test_pre_start.py
@@ -1,21 +1,22 @@
 from unittest.mock import MagicMock
 
+from pytest_mock import MockerFixture
 from sqlmodel import select
 
 from app.tests_pre_start import init, logger
 
 
-def test_init_successful_connection(mocker):
+def test_init_successful_connection(mocker: MockerFixture) -> None:
     engine_mock = MagicMock()
 
     session_mock = MagicMock()
     exec_mock = MagicMock(return_value=True)
-    session_mock.configure_mock(**{'exec.return_value': exec_mock})
-    mocker.patch('sqlmodel.Session', return_value=session_mock)
+    session_mock.configure_mock(**{"exec.return_value": exec_mock})
+    mocker.patch("sqlmodel.Session", return_value=session_mock)
 
-    mocker.patch.object(logger, 'info')
-    mocker.patch.object(logger, 'error')
-    mocker.patch.object(logger, 'warn')
+    mocker.patch.object(logger, "info")
+    mocker.patch.object(logger, "error")
+    mocker.patch.object(logger, "warn")
 
     try:
         init(engine_mock)
@@ -23,6 +24,10 @@ def test_init_successful_connection(mocker):
     except Exception:
         connection_successful = False
 
-    assert connection_successful, "The database connection should be successful and not raise an exception."
+    assert (
+        connection_successful
+    ), "The database connection should be successful and not raise an exception."
 
-    assert session_mock.exec.called_once_with(select(1)), "The session should execute a select statement once."
+    assert session_mock.exec.called_once_with(
+        select(1)
+    ), "The session should execute a select statement once."
diff --git a/backend/app/tests/utils/user.py b/backend/app/tests/utils/user.py
index 4622c2d3f52..891f32a2bff 100644
--- a/backend/app/tests/utils/user.py
+++ b/backend/app/tests/utils/user.py
@@ -42,6 +42,8 @@ def authentication_token_from_email(
         user = crud.create_user(session=db, user_create=user_in_create)
     else:
         user_in_update = UserUpdate(password=password)
+        if not user.id:
+            raise Exception("User id not set")
         user = crud.update_user(session=db, user_id=user.id, user_in=user_in_update)
 
     return user_authentication_headers(client=client, email=email, password=password)
diff --git a/backend/app/utils.py b/backend/app/utils.py
index ff228cbf14e..8e459cffbba 100644
--- a/backend/app/utils.py
+++ b/backend/app/utils.py
@@ -4,7 +4,7 @@
 from pathlib import Path
 from typing import Any
 
-import emails
+import emails  # type: ignore
 from jinja2 import Template
 from jose import JWTError, jwt
 
@@ -109,6 +109,6 @@ def generate_password_reset_token(email: str) -> str:
 def verify_password_reset_token(token: str) -> str | None:
     try:
         decoded_token = jwt.decode(token, settings.SECRET_KEY, algorithms=["HS256"])
-        return decoded_token["sub"]
+        return str(decoded_token["sub"])
     except JWTError:
         return None
diff --git a/backend/app/worker.py b/backend/app/worker.py
index 5e1f7d64e5e..5afbdbb48f4 100644
--- a/backend/app/worker.py
+++ b/backend/app/worker.py
@@ -3,7 +3,7 @@
 from app.core.celery_app import celery_app
 from app.core.config import settings
 
-sentry_sdk.init(dsn=settings.SENTRY_DSN)
+sentry_sdk.init(dsn=str(settings.SENTRY_DSN))
 
 
 @celery_app.task(acks_late=True)
diff --git a/backend/pyproject.toml b/backend/pyproject.toml
index 54415685b3e..04f468551c3 100644
--- a/backend/pyproject.toml
+++ b/backend/pyproject.toml
@@ -35,6 +35,9 @@ mypy = "^1.8.0"
 ruff = "^0.2.2"
 pre-commit = "^3.6.2"
 pytest-mock = "^3.12.0"
+types-python-jose = "^3.3.4.20240106"
+types-passlib = "^1.7.7.20240106"
+celery-types = "^0.22.0"
 
 [tool.isort]
 multi_line_output = 3
@@ -47,6 +50,7 @@ build-backend = "poetry.masonry.api"
 
 [tool.mypy]
 strict = true
+exclude = ["venv", "alembic"]
 
 [tool.ruff]
 target-version = "py310"
diff --git a/backend/scripts/lint.sh b/backend/scripts/lint.sh
index 9dc9ed427cf..148d37c5c0f 100644
--- a/backend/scripts/lint.sh
+++ b/backend/scripts/lint.sh
@@ -3,6 +3,5 @@
 set -x
 
 mypy app
-black app --check
-isort --recursive --check-only app
-flake8
+ruff app
+ruff format app --check
diff --git a/backend/tests-start.sh b/backend/tests-start.sh
index 099c2b39731..53396b6ad8e 100644
--- a/backend/tests-start.sh
+++ b/backend/tests-start.sh
@@ -3,4 +3,5 @@ set -e
 
 python /app/app/tests_pre_start.py
 
+bash ./scripts/lint.sh 
 bash ./scripts/test.sh "$@"