Hello, unity how can I write a javascript or c# code to level up characters in my game.

The type of level up to implement faster running & stronger attacking etc. But I dont know what to do..... I am a beginner, I really want some help!,Hi, I want to implement a javascript code for leveling up my character, so he can run faster attack stronger etc. However, I don't know how to do it.... Could someone show me how to create this script, I would love to learn it.