What advice would you give for someone to get started with freelancing/side projects to earn some extra money?

I started my first job as a junior JS developer a month ago, and I'm quite overwhelmed with all the things I don't know. I feel like the knowledge gap is vast between my colleagues and me.

So what's the best advice you can give for me and how I can keep improving myself. I used to take many online courses before I started, but now my time is limited, and can't watch as much as before :(