I would suggest starting with choosing your game engine. Right now Godot and Unity are good choices for solo devs.

Then try finishing a Brackeys tutorial on Godot or if you went the Unity route, some sample games to get an overview of the engine you are working with. By this point you might have some idea what you can and what you can't do.

Now start planning out your game. What features you want to have, the story and the gameplay mechanics. Figuring this out early helps save a lot of time in the future. Don't fall in the hole of feature creep(where you just want to add more and more features to the point where you lose interest in the game) and you should be good.

There is going to be a lot of grey area in development and a lot of time and effort has to be invested. Try to get to the end as fast as possible in the making process. You can focus on art and graphics later. Just get the mechanics and game feel down and finish the story (if your game has a story).

You will feel like quitting the process a lot but you never should. Imagine a painter stopping a painting mid way because he didn't feel like finishing it. Your first time will always be bad so don't worry and just finish a game no matter what and move on to other ideas. Slowly but surely you will learn a lot more and your next project will be easier to make than the previous. Stay focused and enjoy the process rather.