What subjects should I study at University?
What I needed most in university was math and English. The physics you will learn from scratch again. You will discover that classical mechanics, which you learn at high school, is a much richer and elegant system than how it is taught in school. To experience this elegance you need to learn more math. What was maybe a bunch of tricks and rules becomes a simpler system. The new things you learn in classical mechanics (Hamilton and Lagrange formalism) will be so important that it will guide you through the theory of quantum mechanics.
As for the rest, it is great to have very broad interests. Literature, arts and music are as important for having an intellectual rich life as mathematics and physics.
Chemistry or biology. I did both in high school. Both are not required when studying physics (pass the exams) but as a physicist you really want to know how things work. It certainly gives you much insight in the complexities in understanding nature.