Hello,
JEE Mains and Advance are conducted for admission to NIT, IIT and other engineering colleges throughout the country. The exam requires conceptual clarity and rigorous practice to crack.
So, if you are facing difficulties cracking a question, it shows your lack of understanding of that concept or you might have not practiced it enough.
So, go through the theory of that part once again, get your doubts cleared from your teacher and then practice a lot of question that topic.
There would be some topics which would come easily to you and some other which would take time, so identify your strengths and weaknesses.
Give more time to topics you think you are weak in.
Also have a look at the previous year question papers to get a feel of the level of question asked.

Follow this link for more information
https://engineering.careers360.com/articles/jee-advanced-2020

Good luck