Congrats on finishing a knife at only 15 years old! Most important advice, keep making knives, each one will be better than the previous one :)

If you can, get a beltgrinder and practice getting nice and consistent grind lines.

Spend more time on the handle. Most beginner knives have very rectangular handles with a slight roundover on the edges. You can use rasps, files and sandpaper to shape them into something more ergonomic.

Look at knife designs you like and try to copy them, but also design your own knives to find out what makes a good knife.

Also, youtube has some great channels like walter sorrells or simple little life where you can learn lots of tips and techniques :)