i found the problem when i had again time to check the effect. It was simply somewhere a connection to the enclosure.
But there is another question now:
In the P.U.F.F. BuilDocument (https://guitarpcb.com/product/p-u-f-f-pumpd-up-fuzz-face-classic-fuzz-face-with-modern-features-free-charge-pump/) i have to bias the Q2 collector to (negative) 4.5-4.8V or half of the input voltage. Are these numbers really correct? I have problems to do so with the trimmer and in the forum of musikding, where i ordered the P.U.F.F. and asked at first, i got the answer that they doubt this could be correct.
Can someone tell me that the build document is right or wrong in this point?