Hello @Nodegeld, to answer your question, SEPA has a maximum trade size of 0.25 BTC, and it requires account signing in order for to enable full trade limits.

I will recommend that you read more on wiki for clarification, use the the link below.

https://bisq.wiki/Account_limits#Account_signing 

 Oh I'm sorry, I meant 0.1 BTC. But I have found the crucial setting. Never seen that I can change this limit in Bisq:
https://bisq.wiki/Account_limits#User_opt-out_limits
Now it works. Thanks for your answer.