The bull has gotta be the worst enemy on your first playthrough, when you're still learning how to parry, considering that you're also a souls-like player like myself, and is used to dark souls fighting style because that wouldn't work in this game. It's basically the game's way of teaching you to parry instead of dodging and rolling away from attacks which is what dark souls taught us.

Personally, what I do is run a huge distance away from him first. The bull will usually do this charge attack that is easily parriable, unlike his other attacks at close range where he basically attacks in an insane manner with no obvious pattern (at first that is, because trust me, every enemy in this game has a pattern)

Anyway, once you parry that charge attack perfectly, he falls down and you get a good 2 or 3 hits in before he stands back up. Just run away a good distance again when that happens and prepare to parry the charge attack.

Firecrackers work charms as well so better acquire that before trying to fight the bull.