Hello Rina Ranjan,

Try to make the short goal. First set a target for 3-4 days in which you will have to cover few topics and syllabus. work hard to achieve that goal. Take short break. After that increase your target. 

This is a slow process but can work for you.

Stay Away from distraction.

Watch Motivation videos.

Study Regularly.

Believe in yourself.

Talk to your parents daily.

Good Luck.