Student or Learner
I have been learning English for many years.
I think it's interesting to write an essay by English,
but it's also a big challenge for me.
Sometimes,when I see the test's subject of the essay,
I don't know how to start the beginning of the essay.
What should I do so that I can write the essay easier and with fluency?
Be careful about general introductions- they normally get an essay off to a bad start IMO by repeating the question, not answering the question and introducing irrelevant information.
I always suggest that you write the introduction last, after you have figured out what you want to say about the subject.
Answer the question or respond to the prompt with three solid ideas - write those out more fully, THEN go back and write your introduction, saying what you'll say to support your main idea.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.