If you divide the subjects, you will mainly study only six subjects. You should first look at which subjects are better and which subjects are weaker, and then know where you are before making plans.
Mathematics is more than just doing more problems. Listening and understanding are more important than doing problems. In class, you should fully understand what the teacher says and every step of the topic. If you don't understand in class, don't be busy doing your homework after class. Understand first, then do it, and the efficiency will be higher. You should know how to summarize when you do the problem. Every time you do a question, you should learn to observe its type and recall whether you have done this type of question before. It's best to copy down all the topics the teacher usually talks about in class, which are typical topics. When you do your own problems, you can have a look and compare your own problems, and you will find that we have actually done a lot. However, if you want to get high marks, you must practice the questions, be top-notch in mathematics, and do them every day to exercise your feelings about the questions. If you do too much, many questions will naturally come to you at first sight. You don't have to do a lot, but you must be able to fully understand. The so-called complete understanding means that when you encounter this kind of problem again, you can solve it.
Mathematics is also a very basic subject. If your foundation is not very good, you'd better make up your own foundation first and read all the math books in primary school and junior high school. It is difficult to learn math well without spending more time. Practice more by yourself, and you will get faster and faster when you practice to a certain extent. It is impossible to reach heaven in one step.
Everyone wants to be a generalist, but not everyone can do it. Before becoming a generalist, why not focus on a few sciences that interest you? But that doesn't mean you can't do other subjects. The time for other subjects depends on whether you can work hard.
I am also a high school student now, but I am not a master of all the subjects you are looking for. In fact, there are no masters in all subjects. You can see for yourself. Are the students who are the first in your grade the first in every subject? Those who get the first place in the exam will definitely have one or two subjects that are particularly top-notch, but other subjects are not bad. They don't have to spend a lot of time on top-notch subjects, but allocate those time to other weaker subjects and be regarded as general practitioners by others. Hard work is definitely necessary.
You may think that people with good grades learn easily. Usually, you should observe their class. Without 100% concentration, there are 90%, and that 90% has been accumulated for more than ten years. Of course, there will be dark horses. Dark horses are students who are smart and talented in certain subjects. They may not have to accumulate for more than ten years, but they are sure.
I am full of energy. If you are not particularly clever, study hard and you will get results one day.