Error example:
Cannot delete the app. A field in the app has been referred from a Lookup field "***" in an app "***". Change the "***" field setting or delete the field itself in "***".

Cause:
The app you are trying to delete is referenced by a Lookup or Related records field in another app which you do not have the permission to manage.

Solutions:

• Ask a user who has permission to manage the app displayed in the error message to delete the Lookup field or the Related records field.
  Deleting fields

• Ask a user who has permission to manage the app to be deleted and the app displayed in the error message to delete the app.