I have 91.3 percentile in JEE Mains 1st attempt. Can I get 99 percentile in the next attempt or how much percentile can be increased?

It's difficult to predict exactly how much your percentile can increase in the next attempt as it depends on a variety of factors, such as your preparation level, the difficulty level of the exam, and the performance of other students. However, it's possible to increase your percentile significantly