Hii Chetak!
Frankly speaking, if you haven't studied the whole year, you can't do anything in twenty days. But, if you have put efforts and studied the whole year, a little more hardwork will help you succeed. Make a timetable. For first 10 days focus on the chapters you find tough. Then next 10 days, focus on the chapters you feel easy. Solve as many problems related to the syllabus as you can. Practice everyday. Make small notes and revise everyday. Take the help of your teacher to clear doubts and you are ready to go. Only practice will make you perfect. Hope this helps.
Good luck!