How to prepare a foundation for higher mathematics?

Question

Mathematics

It is necessary to prepare a basis for studying higher mathematics with the prospect of working in the State Duma.
Please tell me how to do it more efficiently.
What sources are better to use to start from class 7 to 11.
I looked in the direction of school textbooks, but in all that I saw I did not like the presentation of the material. In general, without any justification, without clarification, just a dry presentation of the material. Theory is a challenge. And why is it, and where to use it, and how to use it is not clear.
We need materials where the material will be chewed in more detail in order to get a good enough base for further study

Answer 1

The best school textbooks in mathematics - textbooks by A.P. Kiseleva.
Problem solvers are also better to take the old ones. For example, in geometry - Rybkin's problem book.