1. Go to 'cstrike/addons/amxmodx/configs' and open the config file 'grenade_callouts.ini' on Notepad.
2. Copy the texts below and replace the LAST 9 LINES in the config file with the copied texts. Save and exit.

Flashbang.
Throwing a flashbang.
I'm throwing a flashbang.
Grenade!
I'm throwing a grenade!
Grenade out!
Smoke!
I'm throwing smoke!
Smoke!