hi Duyen, thanks for the question 😀
I think the best way forward is if you find a native speaker and work together on pronuciation. You will get instant feedback how to pronouce words/sentences correctly and after some prectice you should improve.
I recommend an app called Tandem where you can find language partners (this is a free way) or Italki if you want to hire somebody.
You must hear a lot, a lots of songs, podcasts, and ...