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?
In my opinion, listening to English is very important, it helps you to feel new sounds and learn them faster.
Besides that, reading a lot will make you have a good sense of vocabulary and grammar.
It is good to cultivate these two skills, as a child who hears enough words by himself will mimic and speak gradually.
And you will get it.
Good luck