Really good idea! The jumping was legit challenging. I made it to the boss, but wasn't really sure what to do? XD Just kinda kept jumping over him and running off the screen.
I think this is a really good start, and its really cool that you want to get into video game programming from a young age!
Some background music and simple jumping noises could have really uppeed the polish for this game! But dont be disheartened! Brackeys has a great tutorial on adding noises which you should have a go at next time :) Also i use a great website for (mostly) royalty free sounds which is a great resource!
Brackeys Tutorial : https://www.youtube.com/watch?v=6OT43pvUyfY
Sound/Music Resources: https://freesound.org/
Keep it up!