The „normal amount“ is zero. Porn is a fairly new invention - talking about the hypernatural, or at least realistic modern form here, not some nude or sex paintings of ye olde - and I think there’s by now enough research that porn does indeed fry your brain.
It’s a bit like talking about „taking a normal amount of drugs“.
That being said, I noticed an interesting dialectic in these discussions. On the one hand, people will always tell you that nofap is crazy and just stop jerking off if you want to, and you’ve got to be an insane loser to become addicted to porn…
And on the other hand nobody believes you when you tell them you never watch porn or jerk off.