Help in GameMaker

Hey guys! What's up? I'm having a weird problem with GameMaker Studio 2 right now. It is not setting some variables at the "Create" event and because of it the game is crashing. How do I fix this?
I am trying to add particle effects to my game, but anytime I try to add a second particle controller object to my room, it displays one of my sprites there, even though the controller object has no sprite and is set to invisible. What am I doing wrong?
So how important is it exactly that my game jam be two player capable? I had an excellent game concept in mind, but it kind of got bulldozed as soon as i read the 'must have local multiplayer capability' part.
Hello. I am trying to make a jump sound affect. I am new to coding. I have a sound, how do I make it play when I jump? I watched tutorials; do I have to enable sound on my game or something? I'm using Drag and Drop.

IDK why my code error i watch tutorial on https://www.youtube.com/watch?v=f9XnGCEuWOA
thare,
