I'm in grade 11 and preparing for IIT-JEE I believe I don't have strong concepts of first 4 to 5 chapters, how do I start from scr

If you want to start your studies from the scratch you can start with NCERT books to build your concepts strong and just keep in mind don't be worried about other students what they will think about you if you ask silly questions and trust me all the students think same way it doesn't matter be motivated and self determined that you have to clear IIT-JEE exam anyhow.