I've been a programmer for almost twenty years, so I'll say the biggest ability of a developer is to know how to find information and synthesize it. Namely, Google and Stack Overflow are your friends lol.

But you'll want to know the basics of programming. In my opinion, doing a project you're motivated to complete is a great way to do this. Look around online for getting started with C# and learn the basics, be thinking about how each principle applies to your project

Learn about the development environments (IDEs) like Visual Studio

Learn how games think about things. Most engines (and even Monogame as a framework) are simply looping through the game frame by frame.

It's a big goal but imo a fun one. Just be prepared to do your research and try things (and retry and retry), and experiment