Hi,
Sample papers are just a glimpse about how the exam could come. You cannot just rely on the sample papers for good marks that too above 95 percent.
NCERT books are considered as a Bible for students. As you are studying chemistry and Maths from Ncert along with the sample papers , You can also go for NCERT of physics rather than just relying on sample papers.
If you don't understand the NCERT physics book, you can go for reference such as Pradeep, S.L. Arora just to clear the concepts.
Along with it , get a read on the previous year examination papers as well.

Hope it helps.
Best Wishes