These are some tips to improve your studying you might not know so you can use your time more effectively, most of the tips are proven by science:
Learn before you go to bed, learning before going to sleep can help a lot because during your sleep your brain makes sure it doesn't forget new memories so try to do a bit of studying before going to sleep.
Link the things you have to study with a memory or create a memory with them, this way you're more likely to remember what you learned because your brain has a strong connection with the memory and thus the learning content.
Don't just study one subject, try to study as much different material at once. This way the studying becomes less boring and you also have more repetition which is also really good.
Test yourself, try to test yourself to see how far you are with the studying, this way you also see what you have to study harder on and if you don't know something you are actually more likely to remember it in the future.
Motivate yourself, make sure you have the right motivation to do something, you can tell yourself that if you study really hard for half an hour you get 15 minutes to do something you really like.
Make sure you are hydrated, especially tea and coffee can make your study performance better.
Take breaks, studying is the most effective if you spread it out and repeat a lot, it's better to study for half an hour three times than to study for one and a half hour straight.
Study with someone else, studying is a lot more fun if you do it with someone else and you can help each other out if you don't get someone.
Don't just use books, there are a lot of ways to study. Find a way you like and that works for you and that doesn't always mean writing stuff down, there are a lot of sites and programms to help you study.
Hope these tips are useful to you!