Cutting my own hair, I’ve screwed it up a few times now. My favorite was when I was just going to give it a little trim, but the guard popped off of the clippers mid-stroke and took a huge chunk out of the side/top of my head. So I was rocking a buzzcut for the first time in 15+ years. Turned out I liked it once I got over the shock, so I’ve been doing it intentionally ever since
It’s just hair, it’ll grow back eventually.
Consider this another vote for Ubuntu or any of its variants. They’re beginner friendly, and established enough that you’ll find plenty of resources written specifically for them. Linux Mint is another one I’d recommend for beginners, it’s designed to “just work” out of the box and be an easy transition for Windows users.
Then it’s just down to using it some. First and foremost, leave Windows installed until you’re comfortable with whatever else you end up trying. Whether you partition, or make a bootable USB drive, or even just a VM, use some kind of temporary space for practice. The terminal is a lot less intimidating when you aren’t learning in your main environment, you can go break things and see what happens.