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It will not be useful to you to know how native speakers learn. There are so many things we do by instinct, because we know it sounds right, because we know if feels right -- there are so many things we don't make decisions about, but just write or speak -- that it would be impossible to explain.
If I said to you "Tell me how to learn Mandarin quickly. I want to speak perfect Mandarin, write it perfectly, understand the grammar and so on" would you think it was possible? People can certainly learn a second, third, fourth language (or more) but it won't happen quickly.
Remember to capitalize the word English every time, and proper nouns, like China.
Leave a space after your punctuation marks.
The best thing you can do it read as much as you can, listen to English radio, watch English television, etc. Pay attention to the way people speak and write.
Student or Learner