Take challenging composition courses (not just creative writing courses, but classes in journalism, technical writing, etc.) so that you can "speak" journalese, UNese, legalese, etc.
You're going to have an essay that asks for an opinion, you're going to have an essay that does not ask for an opinion, and then you're going to have a hybrid, you're going to have a combination of the two.
And while you're talking with them, also ask for feedback – especially if your exam contained short-answer or essay questions where there's no concrete answer.
Yes, I think so, cause as a foreigner my English grammar is not perfect and I got a lot of corrections from American or Western teachers that I now can write a pretty good English essay.