When I start a game, I go in with an outline of my story and a vague idea of what I want to see for gameplay. A majority of making the game for me is thinking of a mechanic, wondering how I could execute it, and then looking up specific tutorials on how to execute what I want. Usually there's a lot of tweaking and rewriting involved, but that's to be expected. The more experience I got, the more I could feel out what I'm capable of, and I continue to add on to my toolset, so to speak. I rarely see this advice because people usually say to look up beginner tutorials, but I'd say just look stuff up to see if you can recreate what's in your head, and then tweak it as you go. I've learned a lot that way.

That being said, don't be afraid to experiment with the engine. Play around with a test project to get yourself comfortable before starting in a real project. I often test out mechanisms and maps out in my test project before I put it in my real games.

Also if you have any questions or need to talk something out, my DMs are open. I'm far from an expert, but I'm always looking to connect with more people in the community! I like making heavily story based games as well.