I feel you, Smriti- I have trouble with focus and concentration too, often in tandem with a lack of motivation. It can be really hard to make ourselves do something (even if we know it’s important or that we have to get it done) when our hearts are elsewhere- like enjoying magick! 
You may know that I really love tea magick and tea rituals- so here’s a tea focus spell with black tea (any kind of black tea should work fine!) that you might find helpful:
The Sun Sigil spell was designed to help with a test or exam, but it can also be helpful when trying to collect focus for studying too:
Additionally, I think it would be out-of-character for me to not recommend one of my favorite crystals for motivation haha- I’m a huge fan of Carnelian! It’s a great stone for boosting motivation and creative levels. Whenever I start to get distracted or feel low energy, I wear a Carnelian bracelet and it helps keep me going. Great stone for creating things and getting work done! 
One more non-magickal suggestion is to try the Pomodoro Timer- the theory is that you work on whatever you need to do for 45 minutes (or whatever amount you decide is best), have a 15 minute break to do whatever you want, and then do another round of your task. Having a video or timer running can help to keep you on track 
Here’s a Pomodoro Timer video on YouTube you might try:
Whatever you choose to do, I hope you can find some ways to help you focus! That way, once your studies are taken care of, you’ll hopefully have plenty of time to enjoy your magick guilt-free 
Wishing you all the best! Lots of love and blessed be 