Pretty impressive for only 3 days. I would recommend being able to sprint, crouch, and aim, as those are pretty common in most FPS games. Also, perhaps you will want to incorporate animations into your game later on, as that would help make the game more immersive.
I also noticed that when you shoot further distances, it sort of looks like you are shooting multiple bullets, so you may want to fix that.
Its really good! Its also very impressive that you got this done in only 3 days. Imma say kinda what @ChickwensRule said. I would add some sprit, crouch, and aim animations so you can shoot from farther or lower distances.
It’s pretty good for a game created in 3 days. Although, my only set of feedback is the game is very cartoony looking. And when it has realistic guns it doesn’t really match very well. I would recommend making more cartoony looking guns. Other then that it looks pretty good imo.