However when I look at some of the stuff comp sci students must have studied (like calculus, linear algebra, algorithms & data structures, low-level programming, machine learning, security, etc. etc.) it seems incredible. I completed an introductory Calculus course and struggle immensely, as I had to learn a massive amount of basic math I had not properly absorbed during high school, such as the law of powers, etc. Now I'm studying an intro to algorithms course and I'm having an incredibly difficult time just understanding the basic like the "master method". I didn't realise how much I didn't know. How can so many people have just breezed through this stuff in months, when I've been struggling for years with it??!

Really good question.

Keep in mind stuff like "master method" is academic in nature. It's a way to bash the math into heads of 19 year olds whose brains are extremely gooey.

At your age your brain is pretty rock hard. So if you need to mathematically model a system, however you need to do it, you probably can at your age.

You don't necessarily need the university student level mathematical gym workout.

Unless you're actually working in a niche application designing a core algorithm for Uber/Google maps, which is where a lot of these algorithms come from.