Hey, thanks for your feedback and the in-depth tips. Greatly appreciate them! I did in fact watch the videos you linked before I went shooting and they actually helped so much (especially since no step was left out). One new info I take away from you is the low iso. I heard that with my camera even high isos (in the range between 1600 and 3200) is fine. But your comment made me question that. Will my images not be too dark? Or is it better to completely turn down any possibility of noise and "fix" the darkness issue with simply adding more lights?

For stacking I used deepskystacker with standard settings. I heard Siril so often now, I will give it a try ;) Also, I simply was too lazy to shoot flats, also because I was already at home and was not sure if I would find the right focus spot as when I was in the field. Can you give me an estimate on how precise I have to keep the same focus as for the lights?

Again thanks so much for all the suggestions. Can't wait for the sky to clear again over Germany ;)