Read simple novels and look things up in a dictionary when you see a bunch of words that don't make sense. Watch shows with subtitles and do the same. Chat with people in the language. This is how non-natives learn English outside of school. It's also how non-natives learn Chinese.

Ain't nobody downloading stuff from GitHub and splitting things into tokens to learn English like the other commenter is suggesting lmfao. But people are obsessed with bizarre and completely inhuman methods like that when they learn Asian languages. I cannot understand why, and it's seriously just Asian languages.