Problems with unwanted drafts

Try using those ultrasound things that some shop owners use against teenagers. Students are still somewhat young...

Cigarette smoke can justify a reduction in rent (for examples see [Mietminderungstabelle]). Just claim it from the Studentenwerk and pay less. Bet you'll get a response quickly...

But of course, that's not the solution itself...

If I tape over the slots now, maybe the fan in the bathroom will help? It runs every time the light was on, about 5 minutes afterward, that probably doesn't help much, but if I don't do something about the smell, I'll slowly go crazy :/

Warning! The fan needs the inflow from the slots. So if the fan turns on, you would actually have to open a window. But that will probably bring the smell back in. Otherwise, the fan doesn't help with the smell. How about asking the smokers if they could smoke in front of the house.

Yes, I already thought about the fan in the bathroom, but there is also a slight draft coming from my light switch in the bathroom, although I don't know if that would be enough. Unfortunately, the dormitory is a large unit of 4 connected buildings, in my building about 75, I don't think I can reach them all. A rent reduction would basically be an option, but I think I don't want to risk my dormitory place because the other housing situation is miserable.

Cigarette smoke can entitle you to a rent reduction (for examples see the rent reduction table). Just try claiming it at the Studentenwerk and pay less. Bet you'll get a quick response...

A rent reduction would basically be possible, but I think I don't want to risk my dorm room because the general housing situation is miserable.

The Studentenwerk will know that and won’t dally long, the next person will be happy to get a place...

I can totally understand that, it would annoy me a lot too.
I would probably look for another room – maybe someone would like to swap with you, perhaps a smoker who doesn’t mind? Alternative: Apply for another room in the complex at the next possible opportunity.

Yes, the rent is unfortunately unbeatable and unfortunately changing rooms is not so easy, if I wanted another room now, I would have to pay a €150 fee. I think I will tape over the slits. Now in summer, when students stand downstairs smoking until 3 a.m. every day, otherwise I really can't sleep. I have a large air purifier in the room and might just get a hygrometer, I hope that I can still keep the humidity under control that way. After showering, I always leave the windows open first anyway, so hopefully everything will work out.