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?
for beginners i think it is not yet applicable for you to read funny or entertainment books, it needs a deeper understanding of the phrases being delivered for you to understand the content. i highly recommend books for kids, news, story books etc.