Selfmade Platformer Script

So I recently made a platformer script for a new game I'm working on. Before I continue I would like to eventually get some improvement suggestions for the script. Maybe I will learn something new ^^ More infos on the project notes.
my project

I have a suggestion, please allow the use for arrow keys, and I would like up and w to be jump instead of space (not both keys pressed at the same time).

Oh sure! Didn't thought of that. It wont be hard to add, maybe I will even add completely configurable keybinds later on after I did the base game.