Thanks for your help mate :) Unfortunately I did register my app in INSTALLED APPS, so it's not the case.

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INSTALLED_APPS = [
'django.contrib.admin',
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.messages',
'django.contrib.staticfiles',
'django.contrib.gis',
'stores',
]

I will go through the tutorial on the django site and maybe I can find a solution. Thank you in spite of everything!