Ok, I am some steps further now.
Current problem:
I installed Digical, Bring (shared shopping list) and more, that, when I want them to log into google to gain access to the calendar or other required stuff, tell me "No Network access", even though Wifi is on and mobile Data are on, too.
What is wrong? My wife needs those apps, and I cannot figure out what is missing. Do these apps maybe try to access Playstore, which I do not use (I use Aurora instead) and so didn't allow network access...?
Any help much appreciated...
Cheers,
Oliver