Ooook, problem solved, I removed the hood (which goes together with the focusing screen. The famous dust specks happened to be on the other side of the glass (inside the camera), so must have been there all the time and I just noticed them today..
straaaange
anyway, now the camera is cleaner, truth is that the inside was quite dirty. I did not try to remove the focusing screen for its cleaning, it was togehter with the hood and did not thing an easy task, at least for me... anyway, thanks Sandeha and Peter for the advices!