Thanks for your links and your help!
I testet the front/sub and the rear/main camera separately. The front camera still works. But testing the rear camera results in a “frozen system”, with this “black screen”:
I had to remove the battery … and had to wait for an answer of the support. Hopefully before christmas yet …
But maybe replacing the rear camera, the flash, too (is it possible to test if the flash isn’t damaged?), the Midframe and the “out-of-stock 
display assembly” would help me getting my FP1 work full functional… [→ correct English?]
Hmm, the more easy way (and more comfortable…) would be to buy the FP2 (but it’s likely having & using the “First Edition”…). If there are persons who want to repair my damaged one for getting a used, but “cheap(er)” FP1… Hmm, maybe this would be worth considering…
Thank you!
webaschtl
Oh, nearly I forgot: another big problem which I have since a few weeks: Battery problems (wrong charging status / battery might be dying)
… more problems than solutions :(ohno: