What do you actually need in order to learn English, or any language?
1. A good enough brain
Here is the thing: if you learned Vietnamese, your brain is already good enough for English. Vietnamese took you ten years. English takes roughly two to three years to get comfortable in, because you have already been through the experience of acquiring a language once.
2. Enough will
You have to want it, which is intrinsic motivation. Or you need a concrete reason such as a job opportunity, studying abroad or settling somewhere, which is extrinsic motivation. One of the two, ideally both, is what keeps the habit alive across the whole process.
3. A good method
Learners today are not short of information the way the previous generation was. They are drowning in it, and the good is mixed in with the worthless. Choosing the right guide matters most, because their real job is filtering that noise and giving you a route that fits you.
Good luck with it. I had my own struggle learning English, which is why I keep writing these.