Dear <his/her name>!
It's been a long time since the last time we sent letters to each other! Are you doing good? I heard that you are going to have an english exam right? Therefore, I have some shares about some efficient learning english ways that I used in the recently IELTS exam. The most effective way I have found that i joined a foreign chat-group and tried to use all of my sense to understand and communicate with them with my basic english and translate tools, but you should not try to depend too much on the translator because by doing this you can develop your vocabulary as fast as posible. In addition, there is another solution to improve your vocab and sentences' coherence as well. It is watching movie with english subtitles, listening to music with english lyrics, and playing game with foreign people. If there are any posibility, I suggest you to change the all the devices in your house to english language. Thus, by contacting and interacting with english daily, there is no doubt that your english will be improved and mastered naturally.
I hope you will reply my letter as soon as you can, If you free I hope u can also tell me about some ways to learn english that you have found by your own.
From your buddy, <your name>
                                                                                                                                          Sign
                                                                                                                                      <ký tên>