Hey there, I find it uncanny that we have quite similar goals and skills. I’m relatively new too, but I think it really depends on your familiarity with unreal engine though. I’ve been going over some tutorials over the past few months to become more familiar with the engine itself. There are a lot of great tutorials on here like the twin stick shooter tutorial, level design tutorial, blueprint communication tutorials, UMG tutorials, particle effects tutorials, etc. Also you can always download the content examples and take a look at the different features and how they do them. Unreal Engine also has their own official youtube channel and they have live training sessions on various topics. However, without a real roadmap you can end up watching a lot of things that you don’t need yet.
If you want to get a prototype done quickly then maybe it’s a good strategy to divide and conquer which you probably understand very well as a programmer. Break your game down into smaller bits - the UI, the game mechanics, AI, etc and list them out and try to finish each part one by one. You might not know how to do them yet, but it gives you specific goals and points you to the tutorials you need to research and study till you finally have a full game.
You can also start out with a Game Design Document if you plan to work with a team, so it’d be easier for others to grasp what your game is about and collaborate. That’s just my own opinion though, I’m pretty sure there are multiple ways you can approach it so it’d be good to hear the opinion of more experienced devs too.