My suggestion is to start small and move on to a bigger game once you’re more confident in your coding and writing skills.
Trying to write a massive game like the ones you see on the COG site straight out of the gate is a recipe for burnout and frustration!
The game jams that take place on itch.io are great for this. They’re sort of low-stakes friendly contests where a bunch of people get together (virtually!) and write something new, and then share it with one another.
Especially useful for beginning coders because:
- They are short!
- Deadlines!
- Community support from other folks doing the same thing!
And in many cases you will also get comments and feedback from other participants on what did and didn’t work well.
@manonamora posted about Neo-Twiny Jam the other day, and that would be a great opportunity to get your toes wet on a very small scale (the limit for prose is 500 words!) while the iron is still hot, as it were.
And wow, isn’t that a mixed metaphor? I don’t recommend using irons while standing in water.
Anyway, Neo-Twiny Jam is a fundraiser for queer charities too–what’s not to like? 
If you do write something short, I’d be happy to take a look at it, and I know lots of folks here are happy to help answer specific “this isn’t doing what I expected” type questions as well.