I am a student who is studying in England. I have tried my best but my grades, especially in writing, often have bad marks. My teacher said that I had many interesting ideas but got problem with my way of expressing them. He said that I did not go direct to the point. I did not know what he meant because in Viet Nam, I wrote in the same way and always got good marks.
There are different ideas and logic systems in different languages. I don't know Vietnamese, but Asian language speakers in English can often seem a bit vague because they organise their ideas differently. In English writing, we aim to make clear concise points, generally one per paragraph. We state the point in the topic sentence, which is usually at the start so that the reader grasps the idea. then we develop the point. When that is finished, we start a new paragraph. Try making a list of points you want to make, then use that list as the basis for your pargarphs and that might make the writing easier for us to follow.