Are there any two player, PvE 'zombie' game modes?

[Profile Name™]

I am new to Garry's Mod and I have no idea what I am doing.

I want to play with my fried on a beautifully designed map, start out with at least a crowbar or maybe all weapons and ammo, find aliens/monsters/zombies throughout the map, possibly find ammo and other loot throughout the map, and either have one main objective like navigating a maze and reaching the destination, or have a set of objectives where I have to do each thing in a certain order.

Is there anything like that? If not, it's cool. I know that all maps and game modes are user created and that the base game is just a sandbox physics mod. But if there is something like this, please help me get started so I can create a server and play with my friend.

Oh, and in case I didn't mention. I am interested in exploring an entire map and encountering monsters everywhere. Not barricading myself in a tiny room.

Thank you.

EDIT: No PvP at all. No Human Players vs Zombie Players or anything like that. Just two friends trying to explore and survive together.

[Profile Name™]

So how do I go about finding horror maps? Do I need to install a corresponding game mode addon to go with it?

Try nZombies, fam. It's great for solo, or coop and up.
https://steamcommunity.com/sharedfiles/filedetails/?id=675138912&searchtext=