There are some Q & A about focus. It is important to be able to focus in order to study, to work and for a lot of others activities.
If uou study, you may use the pomodoro method (there are a few Q & A about ) see link, and a lot other, just google
Set your timer for 25 minutes, and focus on a single task until the timer rings. When your session ends, mark off one pomodoro and record what you completed. Then enjoy a five-minute break. After four pomodoros, take a longer, more restorative 15-30 minute break