If you select “Play Offline With Bots” in the CS:GO menu, here are a few commands you can enter into the console to tailor setup of the game to however you want.
mp_freezetime x (number of seconds the game will freeze player movement before the round starts)
mp_roundtime x (the length of each round, in minutes)
mp_maxrounds x (the number of rounds played until the game ends)
mp_startmoney x (the amount of $’s you have at the start)
bot_quota x (the number of bots able to join the game)
bot_join_team T / CT (what team you want the bots to join)
mp_limitteams x (the number chosen is the number of extra players one team can have over another, before the game automatically evens out the teams)
bot_kick_all (if you want to kick all the bots)
bot_kick_x (x here is the name of the bot you want to kick)
bot_all_weapons (allows the bots to use all weapons)
bot_knives_only (bots can only use knives)
bot_pistols_only (bots can only use pistols)
bot_snipers_only (bots can only use snipers)
There are more, but these should enable you to, for instance, set it up so its you v. 20 bots only equipped with knives, or whatever floats your boat.