HI
I live in south africa and want to know if it is possible to hunt small game 25-100 kgs with the glock 19 which is a 9mm parra
if so what type of ammo is suited for this

I know it's been done, but I wouldn't. I'd want more power, in a pistol G20 in 10mm. But I'd probably take my Ruger Bisley .45 Colt

If you must use the 9mm, I'd recommend a 147 grain JHP loaded to max velocity for the best possible penetration.
Then practise a lot!