How to remove mods from singleplayer

I recently entered a singleplayer game to change my FOV but I noticed some issues. All of the guns have 1000 ammo and survivors heal really fast. I checked my add-ons but i dont have any activated. Even more i dont have any add-ons that can even cause this, all of them are some maps. I probably got this stuff from some server but i want to deactivate it.