Are you in high school or junior high school? I suggest you go to the bookstore and buy grammar books that you can understand, suit your appetite, feel eye-catching and understand thoroughly. If the foundation is not very good, I suggest you buy a grammar book with more examples, so that you can better understand grammar according to examples.

In addition, I suggest you discuss it with your English teacher and see what advice he gives you. It's your teacher. He knows your English very well. His advice will be helpful to you.