Disabling Collision between players

I have absolutely no idea how to disable tthe collision between players for death run and etc servers

Flat out no idea

Lucky you the example code here does it:

copy that code into a file.lua and place it in lua/autorun/server/

That code is old and doesn’t show everything you need. Plus I think deathrun servers use http://wiki.garrysmod.com/page/Entity/SetCollisionGroup

If you’re going to use ShouldCollide, you also need http://wiki.garrysmod.com/page/Entity/EnableCustomCollisions

I would recommend against using ShouldCollide if collision groups do the trick.