Sadly my Pleroma instance at wirebug.ch is currently down. Some migrations failed and now I don't know how to fix it nor do I have the time to look into it... ;)
@timttmy Thanks, I'll give it a try later on. First I have to finish writing the questions for my final final exams... ;)
@timttmy It worked! The only modification I had to make: also save the upload folder and replace it in the new instance.
Well that's what I do when I mess it up. :)