Philip's calculus course is very classic, but the content is a little old, which is suitable for reference books. Rudin's principle of mathematical analysis is an advanced course, focusing on theory. It is suitable for connecting with other advanced mathematics courses after learning the basic course of mathematical analysis, such as topology and multivariate complex analysis. You have studied calculus, so you have some basic calculations. What you need at this time is to strengthen theoretical cultivation. In fact, many textbooks in China are very good and classic. For example, the mathematical analysis of Fudan University, but it has many versions, you can choose the updated version. Everyone who studies the course of mathematical analysis will challenge Jimmy Dovich's problem set, but I don't think we should be too addicted to it. Just do something suitable. There are many scenic spots in mathematics, and many wonderful ones are yet to come. In the third year of senior high school, my understanding of mathematics was completely different from now.