Listen,listen,listen to dialogues and then mimic the sound The last step is talking with native speakers. .and insisting they correct your faults when speaking.

There are upper intermediate English language books with listening material whose purpose is that, going through all the sounds, the intonation and stress rules, etc., it could be a start, although you'll have to decide if you want to pursue North American English or British English.

This doesn't always work but try copying what an English speaker sounds like in Chinese. Then after you can do an English accent in Chinese(Mandarin) I believe your profile says, try bringing that over into your English. This might sound strange or hard to understand but sometimes it works for me when I speak German. I hope this helps