Finally I am able to print and recognized that after switching to the 2nd+ layer the cooling fans start and they are making extreme noise. I canceled my first prints as I thought this is an error beeping from the mainboard but found out (by coincidence) that these are "just" the cooling fans. I checked that and when running at 100% you can of course hear them clearly but the beeping is gone. As soon as they run at lower speeds (about 250 of 255) you hear that beeping like noise.
Any thoughts on this?