Answer 1

One possible version:
Dear Zhang Ming,
     Thank you for your e-mail. I'm sorry to have learned that your friend Liu Gang became angry with you. In my opinion,it was not right for Liu Gang to be mad at you when you refused to play computer games with him. I think you should have a good talk with him. First,you should tell him it is not right for a student to be late for class. Second,you should tell him the importance of study. As students,we should concentrate more on our studies than computer games,because they're not only bad for our studies but also bad for our health. I am sure he will understand you.
                                                                                                                                      Best wishes,
                                                                                                                                                Li Hua