Hello RTCW fans, I really find this game quite unfun at times and I just wanna have fun, but whenever I open my console command and type in a cheat, it says cheats aren't allowed on this server, even though I am in a single player mode? Can anyone help me on this? Do I have to play offline

Cheats only work if you load a map with the /spdevmap command. For example /spdevmap escape1 loads the first map of the game. If you close the game and try to load a save game cheats will not work. You have to load the map you want with this command every time to use cheats.