Sorry for the late reply, it’s been a while. But thanks to the suggestions from @matthewepler, @The_Projectionist and @filmkeeper the trigger is now working. 
Now the next step would be attaching the opal glass-diffusor and getting the settings etc. adjusted. And then there’s also the problem with the blurred left edges on the audio track which still gives me some headaches. I hope closing the lens aperture a little will help to get rid of this. Did someone here have a similar issue in the past and maybe knows what could be the cause of this?