People learn in different ways. Maybe you've only tried the ways supported traduitionally in school? Like reading, listening etc

Other ways of learning is "learning by doing" which might be hard with theoretical subjects, but can be solved by trying to find practical ways of applying what you learnt.

Maybe you need to study to music to relax more, maybe sing songs of what you're learning. Make rhymes, make things stick.

Some people only learn when they can discuss and react of what they've heard in class. Maybe you need to find a study-buddy who you can talk things through with?

The most common fault I've seen people do is when they follow instructions too blindly, for examples if the teacher say to read some certain pages in a book, the student reads them many, many times, but without understanding what was said.
I had a classmate who used to be up almost all nights studying really hard, she still had to redo some classes. I who took pauses, looked facts up in other books, tried to understand the facts, made sure to eat good and so on, did much better.

I'll try to think of more tips. Good luck!

Have you consulted with a counselor or advisor about this? You may want to rule out the possibility of a learning disability such as dyslexia.

If that's not the issue, try going to whatever department at your university does student support. They should have a study skills class or seminar that you can attend that will give you some professional advice on how to study.

Ask your professors what they meant and how to do it.

Is the problem that you don't grasp the material in the way that your instructors present it to you, or that you don't feel motivated to learn/that the topics seem unimportant or impractical?

If it's the former, then I'll echo Thistle and Salome's advice. Talk to your professors and consult with learning specialists. Find out what study methods will work for you. That's not something any of us could diagnose online with the facts that we have, even if we knew the subject pretty well (which I certainly don't), so you need to talk to a "real person" to get that straightened out.

If it's the latter, then the best I can suggest is to take this free year, work in the real world, meet as many people from different walks of life as you can, and see what you want to do with the rest of your life. Formal education isn't for everyone. On the other hand, spending some time in the real world may increase your appreciation for it. You may just need to go out and find that for yourself.

The one thing that has gotten me through school better than any other bit of advice is to cater to YOUR needs in the way that you approach assignments and class work. Whether it's music, the visual or language. If a subject isn't interesting to you and if you are not engaged with the work, it will be evident in the work you submit for evaluation. If that means that you need to push the limits of what has been assigned in order to make it relevant and interesting to you, do so.
I was never very interested in writing the 7 billion-th comparative essay on the themes of X and Y in Shakespeare's (fill in the blank)... so I would pick a spin on the topic that I did find interesting and go in that direction. If that means you end up doing Freudian readings of Pride and Prejudice... or comparing the theatrical techniques of Brecht to Impressionist painting... your professors or teachers will at least have the pleasure of reading a paper that isn't exactly the same as 70 others, and they'll see that you're taking things in your own direction and asking questions that actually do interest you. Seeing connections between different aspects of your studies and interests will help you to think critically and apply skills across different subjects.

Good Luck!