I will give you some tips to learn and improve your English , but to be a teacher you have to take some extra courses as how to teach English for Chinese in particular ,if your students would be mostly Chinese.
Here are some tips to help you learn and improve your English on the long run:
Intensifying those efforts will help you improve quicker and master the language on the long run. Just practice most of the following methods and don't give up or loose confidence. It is a matter of persistence and hard work.
*Reading at your level of comprehension simple texts or books and looking up new words .
* Listening to English through music and possibly reading the lyrics.
* Watching movies in English with subtitles in your mother tongue..
* Chatting with natives online using voice chats or in real life .Mingling with natives is a very good way to be constantly listening to speech in English, even if you don't understand at the beginning.