I have just met someone with a very severe stutter - advice?

I have just met someone with a very severe stutter - advice? Hi everyone, I hope it is alright for me to ask for some advice here, or maybe suggest if there is somewhere better to post this. So here is the background: I have just started at a new school a couple of weeks ago and one of my new classmates has a really bad stutter, I mean it takes literally a few minutes for him to get a sentence out and it can also be quite difficult to understand a lot of the words when he does manage to get them out too. I really want to be patient and polite and listen to him when he's trying to talk, but I find it pretty exhausting. I was able to handle it at first, but now he has kind of attached himself to me, perhaps because I am more patient/able to understand what he has said than the other people in class. So by the end of the day I am quite tired from concentrating to understand what he is saying. He has started to tell me quite personal things, like how he has social anxiety and depression and was excluded from social groups before. The thing is, I am also trying to get used to living in a new city, studying new things and making new friends myself and I don't really want to take on someone else's problems (I know, that sounds harsh!) I am a bit worried he thinks I have endless patience to listen to him. I tried to include him in a group conversation with a couple of other people I get on well with in class, but it was really difficult to hold a conversation because of his stutter and I could tell the others were getting a bit frustrated with it. As was I to be honest because I wanted to get to know these new people as well! Also when I am trying to listen to him, I miss things that others are saying and I get annoyed because I feel like he is monopolising my attention. I know it must be extremely difficult for him to live with this condition, but I need to know how I can effectively and respectfully communicate with him so he knows where my boundaries are. ​ So here are the questions: I find it really tiring trying to understand him - do I tell him this? How? Should I ask him to communicate with me by writing? Is there a way to try to include him in group conversations?