Hii Manish!
This is a very common problem with students across India. Physics tend to be a difficult subject and needs more attention. In order to improve in physics, the only way is to study hard. Practice makes a man perfect. So, you need to set a timetable and follow it strictly. Be full attentive in class and revise the concepts taught in class the same day when you go home. Revise and solve questions related to the concept. Study the next concept to be taught in advance and then, when it is explained in class, you will grasp it more. Solve your doubts with the help of your teacher and just practice, practice, practice. Hope this helps.
Good luck!