1. Create a local server via main menu (Practice with Bots or Workshop Maps).
2. Select Competitive or Custom mode.
3. Join Terrorists.
4. Open your console and type

sv_cheats 1
bot_kick
mp_autoteambalance 0
mp_limitteams 0
mp_startmoney 10000
mp_buy_anywhere 1
mp_round_restart_delay 0
mp_buytime 3600
mp_freezetime 2

mp_do_warmup_offine 1
mp_do_warmup_period 1
mp_warmuptime 3600

mp_t_default_primary "weapon_ak47"

bot_join_after_player 1
bot_quota 5
bot_join_team CT
bot_knives_only
bot_dont_shoot 1

sv_infinite_ammo 1
mp_restartgame 1

This will give you a warm-up with harmless bots which immediately respawn when they are dead.

1. Open your Windows File Explorer
2. Navigate to your Counter-Strike: Global Offensive config folder
(C:\Program Files (x86)\Steam\steamapps\common\Counter-Strike Global Offensive\csgo\cfg)
3. Create a file with the name "botaiming.cfg"
4. Paste into the file the commands

sv_cheats 1
bot_kick
mp_autoteambalance 0
mp_limitteams 0
mp_startmoney 10000
mp_buy_anywhere 1
mp_round_restart_delay 0
mp_buytime 3600
mp_freezetime 2

mp_do_warmup_offine 1
mp_do_warmup_period 1
mp_warmuptime 3600

mp_t_default_primary "weapon_ak47"

bot_join_after_player 1
bot_quota 5
bot_join_team CT
bot_knives_only
bot_dont_shoot 1

sv_infinite_ammo 1
mp_restartgame 1

From now on, you can activate the previous commands with one console command.
exec botaiming

Don't forget :)