Hello,

You are in 12th class student so you will give JEE Mains examination 2022. Which is almost coming about within 1 year or less than that. Situation depends on covid ofcourse.

Main thing you have to do study very well you physics chemistry and mathematics in 12th from NCERT books or whatever you have for JEE Mains examination. Then you can know which chapters are easy for you and which are not. Try to every chapters easy for you in 12th class because you said that your 11th is not so well. After practicing some mock test of 12th class you can study 11th class physics chemistry and mathematics also. Those chapters are easy for you, you can study properly them. And giving mock test practice MCQ for it. You will get good rank if you follow this.

All the best.