How to learn System Design as a recent graduate?

A little background here: I'm a final semester student currently going through final stages of my internship. Having worked on a few projects, I've noticed tackling the requirements is not that much difficult but there's a good Software Engineering emphasis on the "how" code should be written as more readable, reusable and in a more professional manner.

This took me on a parallel exploration based on the intrigue for design patterns and I'm 3/4th of the way for Design Patterns by Refactoring Guru ebook with implementing almost all of the examples in mostly Java but a few in C++ too and what I'm thinking is most likely the next step is to go for System Design.

So here's what I truly wanted to ask:

1. Is the next step System Design here?
2. Where should I learn it from? Free on YouTube, course, github/websites, blogs or books even?