Today I knew the fact that I cannot improve my English only by reading my major books.
There are some reasons. One of them is that in major books I cannot see the questioning sentences. And many English tests such as TOFLE, TOEIC and GRE do not deal the questioning sentences. But it is not so easy and when we meet a new person, we have to ask many things. It is obvious that I cannot improve how I can ask by reading text books. Second of the reasons is that in major book the subject be never 'I' or 'you'. But in daily conversation, we always use them. Third of them is that in major book all sentences use present tense. But in dialog we have to care the tense.
I, subsequently, found that I have to schedule to study English. I don't think that my English will be autonomously better only if I live in U.S.A. And I think I need some materials such as English conversation. When I took some conversation classes in Korea, I though that those classes are useless and are wasting of money. But now I changed my mind. It is really necessary.