@Anathematika Welcome to hyperPad. :)
As actually mentioned, you can use Collision Event to trigger behaviors when colliding with another object. So when your player collides with a gun, you can trigger logic to:
Remove the gun from the scene
Make your player hold a weapon (could be a simple sprite change).
And enable the ability for the player to shoot.
Of course, if you want more customization than what is provided, you are free to use any other behaviors than the preset ones. For example, you can use the Raycast Test behavior if you want bullets to register instantly. Or you could have a graphic of the gun be attached to the player, then you can swap the graphic or change its visibility when the player switches weapons, unequips it, etc.
Pretty much everything you can do in a 2D game is possible in hyperPad. You'd have to break big tasks into smaller steps to achieve what you want. Feel free to ask for anything specific! 👌