Sir every concept of physics cleared by me but i am not able to do some questions. Why?? This is happening? What's the problem?? Please answer sir.

Dear Student
There might be an issue like:
* You might be solving harder problems initially. My advice is that don’t go with higher level problems initially,Go step by step.Try out some easy problems through which you understand the concept thoroughly and then go for hard level problems.
* You might have not understood the concepts thoroughly,go through the concepts thoroughly and then try out some problems

Thanks