Im a lvl 31 Fighter
I use a sword 11-119dmg
and a armor 23-70def

i can kill like 1monster in the arena then i have to reg
and if i cata i lose life very fast

what can i do to make this better?
so maybe i can kill 5-10 monsters

my stats are

str:54
dex:80
int:14
vita:50

Buy a level 30 weapons with 100+ enhanced effect if you want to get close to 5-10...
On a more practical nope, try to cata the first few times with a full group of 5