Tried this again, same result like before: ending up in the frozen FP-logo-screen.
Name is “IMG-e-0.21-q-20220122158537-stable-FP3”.
Should I try to install FP OS and then again eOS? Im really frustrated and kinda helpless here and I want to put an end to this situation, preferred today.
I finally made it, such a relieve!
I found out I used the wrong files of eOS installation (didnt knew that I need dev-version, thought stable was the way to go - well, I was wrong, due to my newbie stat. Learned something new today, the hard way.
Nothing to do with that. Stable should work for a new install as well as dev.
But … whatever works 
.