Listen a lot, write a lot and speak a lot. Reading is also important. My usual approach is to watch English YouTube videos when I’m on the platform. I specifically look for English content. I avoid Vietnamese videos on YouTube Polly because the information isn’t always helpful and there’s a wealth of useful content available. By watching these videos, I gain valuable information and simultaneously improve my English. If you’re able, try watching English videos on YouTube. This will help you get used to English pronunciation. If you encounter something you don’t understand, simply look it up in a dictionary.
Forget about English and foreign language if you are already 50 years old, there was no point of learning any language when you are already that old. It is not that learning language at your age is no longer useful. It is because they're more useful things you can learn and you should learn when you're rich that stage of life. As you get older you must know time is getting more and more valuable now so spend those time wisely don't spend the time to learn English because the benefits that English language can bring to you at your stage of life is very minimal.