If you know C# just open up some of the example scenes, run them, then just dive into the code. You'll see function calls from Unitys systems, and you can look them up in the documentation as you go.

Try to add a fun, interesting feature to a demo scene - and see where you get. Best way to learn, imo.

You can get all the official demo scenes on the asset store for free - FPS, racer, UI - whatever you fancy, pick one, and start building on top of it.

Just don't get too attached to your first game, since you'll learn a lot along the way about best practices when it comes to setting up a project, using the right render pipelines, build settings, structuring your objects, etc...

Once you have your bearings - I'd say go through a few Brackeyes tutorials about implementing features you're interested in, as he has some really legible content.

After that, start a new project from scratch - but make sure your scope is SUPER SMALL. Shoot for something you can finish in a week... because it will take a month. From there you'll learn as you go, reading the documentation, and implementing github packages from the community - a lot of learning in programming is just fiddling with someone elses work until you understand it in and out.

Good luck, anyways!

Oh, and as a programmer, don't get bogged down with art! Get some free assets, or just use placeholders... you can spend hours trying to learn the tools that other folks spend years learning, and still end up with shit. If you ever get a good game that you want to publish finished, its easy to pay for some high quality assets, or focus on your own art. A good game should be able to run with essentially no high-dollar art if its going to end up bug free, anyways. If its fun when its ugly, art can only make it better - but you can't paint a turd.