Hey Codeforces Community, I am kind of stagnant at the pupil rank as of now. But now I feel that I should start learning the stuff to get started with basic CP. So, is it okay to start with number theory and mathematics? If yes, what are the resources that you followed or suggest. If no, where should I start on with?

Also, what should be the strategy going forward from this point?

My present situation: Can solve 800-1200 rated problems easily. Know basic Number Theory, maths and implementation.