Hello Rohit, this is a very common problem now a days. The best way to focus during studies is to keep the phone away and enjoy what you are reading. Go deep into the meaning of the book and try to understand the bigger picture. Don't study while keeping only marks in mind, try to study thinking about the meaning behind it. Imaging yourself from 10 years now and think that if you could have just not addicted to your phone and other things then you would have been a successful person. Then you will understand the reality and then you will study with more focus and determination.