How to make a weapon, attach it to the player (2D Top Down), make a bullet, and use an input to execute the bullet

Godot Version 4.2

I am trying to make a 2D top down game similar to Archvale and i am having trouble on attaching a weapon (lets just say a gun) to the player and using the mouse cursor to make the gun look at it from all directions. I have tried watching tutorials but they all make the gun not stay in place and crashes when trying to shoot a bullet by input.

Any help will do, and thank you.