Hello student you've more than 5 months for Jee main from now so be positive, you'll definitely crack Jee main 2021 of you prepare with determination and consistency till your examination. Prefer NCERT to build your basic concept and make sure you solve each and every example and exercise questions of NCERT. After completing NCERT thoroughly refer to the reference books as mentioned below

Concept of physics by HC Verma

Op Tondon Chemistry

Rd Sharma for Mathematics

Arihant practice book for Jee main.

You can also subscribe to careers360 knockout package for preparing and qualifying Jee main entrance examination in first attempt.

Refer to the link mentioned below - https://learn.careers360.com/knockout-jee-main-april/

Feel free to comment if you've any doubt

Good luck