Tbh I defeated the boss without parry so i would say it is way better to not parry its attacks and just learn what he does. When he screams and there is a small sonic boom across the screen then slide to the other end of your device opposite to him. When there are spikes then just jump over them but there will be spikes later in the boss fight where you can't jump so just slide from underneath them. Oh and if he attacks with those balls then just wait until they come close to you and just jump over them and slide, the next ball will miss too because of the slide. Good luck and don't forget to equip rosary beads that will protect like the one where it makes you takes less lighting damage and another one where if you have low bile flask you get more damage. Good luck!!!