Start with some tutorials. Any tutorials honestly, as long as you complete a small game. Keep it small initially even if it seems boring. Follow them to the word, the purpose for you to understand the engine and the tech stack. Then jump to a few other game tutorials while studying programming, specially game dev related DSA and design patterns, gradually experimenting with your approach rather than blindly following the tutorials.
btw, both Unity and Godot are great, but both have their place. Switching is not impossible, better you start with what you want to stick to in the long term. You could at also go for Godot.Net (C# version) as that might make it easier to switch between the two if required in future, but unfortunately you won't find much tutorials and even community help for the .Net version.
