***** NOT A TEACHER *****
I personally would change that question to something like: "How can I improve my ability to write essays and proposals in English?"
I believe that many writing teachers suggest the following:
1. Read widely in your chosen field (medicine).
2. The "secret" to good writing is revision.
a. That is to say, many people think that they can simply sit down, write something, and then send it.
b. Good writers write many drafts. That is, they write something and then check it for grammatical mistakes and for unnecessary words. Then they do the same thing again. And perhaps they do it again for a third time.
i. If you write 100 words the first time, maybe by the third time, your paper will be down to 60 words.
Student or Learner