A) i live in Almaty. How long...
B) i know Dmitry. How long...
C) Omar is learning German. How long...
D) i'm waiting a letter. How long...
E) I'm waiting for my friend. How long...

a) How long have you been living in Almaty? b) How long have you known Dmitry? c) How long has Omar been learning German? d) How long have you been writing a letter? (У тебя ошибка в вопросе правильно не waiting а writing) e) How long have you been waiting for your friend?