farukqmul
How to improve critical reasoning skill ? I have gone through many books and solved questions but still I can't score well..Please suggest me...

You just have to practice. There's no way around that. Keep track of what types of mistakes you're making and pay attention to that when you're taking practice exams.
To help with CR in general though, it might be useful for you to start reading English news websites or English literature books. Those have more vocabulary words that you will find in the Verbal section and you'll get used to reading them and understanding them.