Hi

Some of the  important topics or chapters based on their weightage in past year JEE examination is given below subject wise, you should stress more on these

PHYSICS

Modern Physics -20 marks
Heat and Thermodynamics-12 marks
Optics - 12 marks
Current Electricity- 12 marks
Electrostatics- 12 marks
Magnetics- 8 marks

CHEMISTRY

Transition Elements and Coordination Chemistry- 12 marks
Periodic table and Representative Elements- 12 marks
Thermodynamics And Gaseous State- 8 marks
Atomic Structure- 8 marks
Chemical Bonding - 8 marks
Chemical And Ionic Equilibrium - 8 marks
Solid State And Surface Chemistry - 8 marks
Nuclear Chemistry And Environment - 8 marks

MATHEMATICS

Coordinate Geometry-20 marks
Limits, Continuity and Differentiability-12 marks
Integral Calculus:- 12 marks
Complex numbers and Quadratic Equation :- 8 marks
Matrices and Determinants:- 8 marks
Statistics and Probability:- 8 marks
Three Dimensional Geometry:- 8 marks
Vector Algebra:- 8 marks

You can get chapterwise weightage for all the chapters for each of physics Chemistry and Maths by going through

https://engineering.careers360.com/articles/jee-main-syllabus-weightage

Thank you