Hello Jignesh,

The main thing is that you have to build your concentration level, then only you can stay focused on your goal. I would like to say that please limit the study time between 10 to 12 hours and please increase your concentration and speed of reading, understanding and solving the problems then you will not face any kind of difficulty.

For preparation of exam, the most important thing is your confidence after that we talk about syllabus. You should know the whole syllabus of BITSAT exam. Your basics in Physics, Chemistry & Mathematics should be very clear upto 12th std. You should read the NCERT books for basics. Then HC Verma for Physics, RD Sharma for Mathematics, OP Tendon for Physical & Inorganic Chemistry, and Organic Chemistry of "Arihant Publication" for detail or extra knowledge. 

You should also try to solve the previous years question papers, this helps too much and you should also give the mock test to rectify yourself and build your confidence level.

Thank You

All the best