Learn English before emigration.

Go to the community college in your state to study ESL. There will be an exam after registration. According to the test results, you can go to the corresponding class to study ESL. After one grade, you can go to the next grade. If you fail, you can repeat it.

ESL will greatly improve your English. In addition, watching more American movies can increase the sense of language.

As for the online learning website, ESL will teach grammar or something, but the words are up to you. I have memorized words for a long time on a website called scallop net before, and I think it helps me a lot. But it still depends on someone. What may be suitable for others may not be suitable for you. You can have a look.