To my understanding there is no offline mode to play the game, but there is a shooting range where you can practice using certain guns and run around and understand the key bindings better. No enemy AI in the shooting range just targets

use my mod, GOM 4, to play offline. it comes with a workshop tab similar to RO2 so you can choose a map and setup how many bots you want with difficulty settings

AWESOME-tHANKS!