So I suggest you find a teacher who is good at math at school. You ask him to help you analyze your defects, whether your knowledge is not solid, whether there is no solution, whether there is no solution idea, and whether you are careless in calculation.
After the analysis, he will have a targeted solution.
If he really suggests that you talk about sea tactics, then you can ask him to help you sort out the classic questions and corresponding variants. Personally, I think methods are the most important. Let me ask you a question. First of all, your analysis and problem-solving ideas must be correct in order to sit down. The old teacher has accumulated a lot of experience in this field. You can ask him to guide you. I think if an old teacher really wants to help you, your grades will improve very quickly.
If you can't find such a teacher, then you can ask the sea tactics yourself. I don't recommend making up lessons, because making up lessons is only suitable for people with very poor foundation. The teachers there are just trying to make money and will be fooled. For them, a one-point promotion is also a promotion. Don't waste time on making up lessons. It is more reliable to find teachers in your own school.