privatekon However, for apps like "Miles" or "ShareNow" I can't get the location to work.
I recommend reading this section of the Sandboxed Google Play usage guide:
If you don't use Google Play Location, you're having your location re-routed to the OS, which is not going to be as accurate, will take longer to get a lock, and apps might not expect it to behave in this way and may misbehave in turn.
privatekon Also, I get notification from my main profile on my second profile, but it doesn't work the other way around.
Make sure you've enabled the cross profile notification from the second profile as well. You need to enable it for each profile separately, and you'll get notification for each enabled profile in whatever profile you are at the time.
privatekon And third (let me know, if I should create separate threads): Is it possible to set apps to global? E.g. I would like my notes app to work on both profiles.
You can install apps in multiple profile. If you've installed an app on the owner profile, in the user profile menu there is an option to "install available apps" which allows you to install apps you've got installed in owner in whatever user profile you want without having to download an app store or anything on the other profiles.
I hope this helps.