I live in a dormitory in Russia with two more roommates. One of them is a nice person so we can take him out of the question. The other one is a problem, though.
He moved in last September when the previous roommate moved out. For a couple of months everything was fine - he was an ok person, cleaned our common room and so on. Later, I started to notice I have several issues with him, first and foremost is him vaping in our room. I told him that I don't like him vaping in the room but he always answers in such a manner that I feel myself dumb but cannot object properly. In addition, he stopped cleaning the room and it makes me uncomfortable because I want to live in a clean environment. Furthermore, we have only one normal-size desk in our room and it's the only workspace that I can use because I don't have a smaller-size desks (like my roommates) provided by dormitory. And today we had an argument about opening a window at night: his place is near the window and mine a little bit further and when it gets too hot at night and I try to open the window he closes it back arguing that it's winter and it's too cold for him (though he sleeps without much clothing and under a thin blanket).
As I already mentioned, I tried to talk to him without much success but maybe I'm doing something wrong. I still have one leverage - vaping and some other stuff are prohibited by dormitory rules so if I cannot get anything from him I can inform the head of dormitory about this and he will probably have to move out though I hope it won't get up to this point.
So ultimately my question is how to make my roommate to adjust his behavior? I just want to lead a comfortable life and I don't want to feel like a pushover.