$1)$

`->` The email is mainly about Peter's trip to the Chinese camp and what did he do there.

$2)$

`->` He has been at the camp for two days.

`+)` Dẫn chứng: I just arrived at the Chinese camp two days ago...

$3)$

`->` The thing that Peter likes most about is nobody ever gets angry or annoyed with him.

$4)$

`->` them refer to Peter's  daily activities, new projects and some of his great friends.

Dẫn chứng: In my next letters, I will tell you more about my daily activities and new projects as well as some of the great friends I have just made.

_____________________

$#Rosé$