How to Defeat the First Boss
The hurtboxes for the wolf are only its whole body when it is doing the red eye charge or if it is spinning to win. The regular three part lunge puts the hurtbox on its head and is perfectly safe from any side that is not the head, and when the wolf isn’t moving, it won’t cause any damage at all.
So basically you want to either bait a dash or a three part lunge, and then dash so that it places you to the side or behind the boss and then belt it in the side with a few swings (greatsword is more efficient here). Boss transitions are usually also free damage unless the game remembers to lock you in place when they happen.
Don’t forget to use your ammo and dark attacks when you can (the rune that boosts nighthowl damage makes it more damage efficient than the purifier until later upgrades), since their burst damage is pretty decent in the rare moments when you’re not being shot at and this boss leaves openings in their attacks that will not be seen in most later bosses.
The wolf is immune to poison for some reason, but grenades are also quick tosses at targets that have really large hitboxes.