How to learn languages?
Many people, children and grown-ups ask me how to learn new grammar and vocabulary. And I always say that to remember things one needs practice. More practice.
To remember vocabulary it is necessary to learn it by heart and then (not to forget) practice it talking, reading books, watching films or short videos. It is also useful to make up one's own sentences and learn them.
To my mind, to rememer grammar rules and structures it is still necessary to make lots of exercises in writing and lots of exercises orally, and of course practice grammar in the same way as vocabulary.