One possible version:
Dear Bill,
     How is everything going? Something is troubling me very much. So I'm writing to ask for your advice.
     I'm going to study in the senior middle school in September. I can live either at school or at home. But
I can't decide because both have advantages and disadvantages.
     At home, I have my own room. So I can have a good sleep. However, I have to share one room with
5-6 students at school. Maybe I can't sleep well. It's a problem. Although I can have better food at home,
I enjoy eating with my classmates. I think it's great fun and I can make more friends. If I live at home,
I'll have to ride to school. It's a waste of time and not safe.
     It's so hard to make a decision. I'll be very glad if you could give me some suggestions.
     Please write back soon. 
                                                                                                                                      Zhang Lin