Don't rush for success, it is certainly impossible to improve greatly in a short time, but if you persist, your grades will definitely improve.
Read more high-scoring compositions and explore a set of writing templates yourself. Look at other people's compositions, pay more attention to the analysis of the structure of the article, how to start, how to end, and how to make sense. When writing your own composition, you can conceive the content in advance, and the accumulated composition materials must be skillfully used.
I hope these suggestions can help you!