I think your brain is a bit overstimulated right now. You need to cut down on everything that gives you fast dopamine, like junk food, social media, TV, listening to music, and chocolate. Do a dopamine detox for a week or 2-3 days. Enjoy boredom on those days. You can practice meditation daily; it will help you.
When you start studying, don’t procrastinate; just do it. Make a to-do list early in the morning or night before going to bed. You can study for 1 or 2 hours, then take a break of 10–20 minutes. If you complete everything on your to-do list or complete most of the things, then reward yourself with something nice.
The most important thing is to stay away from fast dopamine.