Problem with some Apps from Amazon-App-Store

I want as few google as possible, so I decided to go for F-Droid and the Amazon-App-Store.
F-Droid is too incomplete and even at Amazonsome good German Apps are missing , like the “Bahn-Navigator” - but even some Apps which can be downloaded, cannot be installed correctly.

I chose “Easy-Taxi”, “*Bank-App”, “PayBack” und “PayPal” and they can be downloaded - when I try to install them the phone simply states:“not installed” - no reason and no hint what went wrong.

I already allowed “Apps with unknown origin” in the settings - what else can it be?
Any ideas?

It is possible that these apps need Google services running, so they cannot be installed without having Google installed too.