For your first game I could say you did a lot of progress, you got the controls working, although the actions of picking up the gun got bugged out sometimes. 

The story was sort of minimal would have liked a more fleshed out story since it has world exploration. 

Really liked those final scenes with the toy in the darkness it was creepy, would have loved to see more of that inside a house or something, would have made it very atmospheric! 

The gun worked, and the zombies died which is good progress, although It wasn't needed as long as there was an interesting atmosphere and a good story. 

As for sound id recommend watching a few videos on sound design, And I can recommend a few places to make music for free that are cool and I bet you would have fun with! :3 like Soundtrap 

Aside from that good effort!