Dear Alex,
I was so happy to get your letter! I am sorry I haven't answered earlier but I was really busy with my school.
You asked me to tell you about my apartment. Well, there are 4 rooms. There is a very large and comfortable kitchen. Also I have my own room. And it is very well for me.
Unfortunately I'd better go now as I've got a lot of homework to do. Keep in touch!
All the best,
(твоё имя)