Question

подскажите как начать и закончить письмо,
что в основной части писать знаю

Answer 1

Покажу на примере.
Начало:
Moscow
Russia

Dear Hale,
Thanks for your letter. It was great to hear from you. Sorry, I haven't written for so long, I've been really busy doing my homework.
Well, you ask me about... Пишешь основную часть, т.е отвечаешь на поставленные вопросы.

By the way, ..задаешь 3 вопроса другу.

Заключение:
Anyway, I'd better finish now- I've got a lot to do. Write back soon and tell me all your news. Do say Hi from me to all your family and friends.

Take care,
Eliza.