There is no problem with models.py. This is just how Django works. Every time you create or change models.py, you need to run makemigrations to create a corresponding “migration” file. The problem is (essentially) that you keep deleting that migration file after it gets created, so it needs to be created over and over again.
Based on what you wrote in your first post, the partners app is installed correctly and is detected by Django. I don’t think you need to worry about that at this time. If it were not installed correctly, you would be seeing different errors - specifically, you wouldn’t see any errors about partners at all, because Django wouldn’t know about it.
If you aren’t familiar with how Django apps work, it would be helpful for you to work through the Django app tutorial first.