I will immigrate to America in three months. How can I improve my English during this period?

Self-study for three months can also have good results. Buy a basic vocabulary book, the first step is to remember words, don't think of yourself as a person:-), recite 500 words a day and three or four thousand words two days, which is enough for initial communication. You don't need to remember all of them. The key is to repeat the recited words one day, review them the next day and review them once every two days. The second step is to buy a sentence pattern book and memorize the sentences used in the dialogue, and then it's almost done. Watching TV and only watching CCTV9 will give you a better sense of language and a more reliable tone of voice. If you are unhappy with your study, you can go to New Oriental or ask a teacher for guidance.