Ok,
I made some settings adjustments in the slicer and it solved my problem. Being an absolute newb in 3d printing maybe has some advantages. 
What I wondered was that the print always failed at the same point, either the line line right before the bridge of the hole or the bridge line itselt.
My first idea was acceleration and travel speed, so I reduced them to 200mm/s and 1000mm/s². I got the exact problems as before.
Next I disabled Slow down for overhangs and massively increased Bridge speed t0 200mm/s and all the artifacts had been gone.
From the damage to of those affected lines, I guessed it might be some filament oozing out of the nozzle and hardening too fast and either ripping the layer below apart or at least preventing the actually printing layer to stick. So I reduced the time spent for bridges and overhangs, fan speed settings might also help to finetune, but I left mine at stock.
It is just a guess, I would need a much better camera with lots more fps to validate this, but at least I can print this STL now. Its not perfect yet, but at least a good direction to improve on.
@T_guttata Would be great if you could validate the settings and get your results here as well
