The main thing here is probably to learn to be a stronger student.
Show up for class on time or a bit early. Sit in the front if you can. Always pay attention. Ask questions. Keep way ahead in your homework and reading, and always get all of it done. If you are unsure about anything, ask for help.
Start your homework early. It is preferable to start your homework the day that it is assigned. There are several advantages of this. One issue is that if you start your homework early, you will learn a bit from trying to do it. If the only thing that you learn is “I do not quite understand this particular concept” even that knowledge may help you learn a bit more in class the next day. If you start your homework early, and if there is something that you can’t do, this will give you time to ask questions and seek out extra help. Also, some homework will take longer than you expect, and if you start early you will have time to finish it.
You are allowed to do homework on a Saturday afternoon. I still remember doing this when I was in graduate school, and really should have been doing it more often as an undergraduate student.
In math, do not just memorize formulae. Instead, make sure that you also fully understand the concepts.
In learning a language, make sure that you find a chance to use it outside of school. Watch movies or TV shows or online videos in whatever language you are trying to learn. When I was studying French at one point I had a dejeuner francais with some friends and we would attempt to have a lunch once per week where we only spoke French. While we might not have been very good, just trying to use the language can help. I similarly used to watch hockey games in French which helped. Of course if you are learning Spanish instead there are Spanish language channels on TV, and I expect that Netflix and other streaming services will have lots of shows in Spanish.
In literature you need to spend the time to read, and read, and read. The same could apply to history.
Here is a secret: If you get to attend a highly ranked university they will be tough also. Some are harder than others. Caltech, MIT, and Chicago have reputations for being tough, although I found Stanford to be a lot of work also (this was for a master’s degree, so at least every class was in something I liked and it was for a shorter length of time). There is an old saying: “Be careful what you wish for, because you might get it”.
I think that job number 1 right now is to learn how to be a stronger student. This is a skill that will help you for a long time (particularly since skills for being a strong student have at least some overlap with being a strong employee).
In graduate school I learned an important lesson: Putting in the hours of work to be a strong student can be less stressful compared to the effort to worry about the work that I was not getting done. I wish that I had learned this earlier.