No worries at all
Since you said you had a reasonable understanding about C# Monogame should help you get up and running quickly. While not a game engine itself, it provides some decent infrastructure to build games with. There are numerous tutorials lying around on the internet that can be found using your favorite search engine. As Monogame was designed to be a drop in replacement for the now deprecated Xna framework usually tutorials for Xna will work in Monogame with some tweaking.
There are other options for C# which can be found online as well. These vary from full engines to just a simple graphics wrapper - leaving more or less work for you to do on your own. After gaining experience with a few small games you should have a better idea regarding how to best move forward.
Just make sure to keep things simple at first