what should my strategy for jee advance in these 40 days

You should be focused to crack your exam. You should refer previous year papers to understand the pattern and level of questions.

Focus on improving your problem-solving speed, which requires continuous practice. Solve as many as MCQs for your practice.

You can refer below recommended books for your preparation

Mathematics:

Make sure you can solve problems from the NCERT class XI and class XII textbooks.
For best concepts, use IIT Mathematics for JEE (Main and Advanced) by M.L. Khanna
For the most abundant supply of difficult questions: New Pattern IITJEE Mathematics by Dr. S.K. Goyal
Plane Trigonometry and Elements of Coordinate Geometry by S.L. Loney

Physics:

Concepts of Physics, Volumes 1 and 2, by H.C. Verma
Problems in General Physics, by I.E. Irodov
Fundamentals of Physics, by Halliday, Resnick, and Walker
Understanding Physics for JEE Main and Advanced (series), by D.C. Pandey

Chemistry:

Study the NCERT chemistry textbooks for classes XI and XII.
Organic Chemistry, by Morrison and Boyd
Numerical Chemistry for JEE Main and Advanced, by P. Bahadur
Concise Inorganic Chemistry, by J.D. Lee
Modern Approach to Chemical Calculations, by R.C. Mukherjee
Physical Chemistry, by P. Bahadur.
organic, physical, and inorganic chemistry books by O.P. Tandon