How can I increase my concentration while studying?

Location is important. Find a quiet space where you aren't going to be distracted by your phone, or notifications on your laptop, or TV, or people talking in the other room, even if it means going to an inconvenient place. Get that space and know that when you open your book, that's study time and everything else will wait. Then, a lot of focus is just built by habit. For example, if you have a hard time focusing for three hours, start with planning to be focused for half an hour, then work up to being focused for 45 minutes, then for an hour.