How to study well English grammar?
My advice is to learn English grammar through books. You should read children's books and English books. If not, then you should buy bilingual funny books to read both entertainment and remember the grammar structure used inside. From there, learn, take notes to apply when needed.
And, what is your advice?
I guess, the best solution is to talk to natives as much as possible. There are lots of examples from my own experience to follow.