thanks for sharing the picture!

I did attach a heatsink  directly on the sticker and it definetly helps. But the PSU is still loud ... actually I put a second heatsink to the left of the sticker because that part was getting hotter. Now I can touch the heatsinks and they are warm but not hot (they have also attached fans).

other solution I can think off is puting the PSU on mineral oil ... just the PSU

or maybe run it at 75% and use a supplementary PSU