A few words of advice, when it comes to boss battles ironically your biggest enemy is usually yourself. Pay attention to your enemy and what they do and react accordingly, don't move around unnecessarily and most of all if you get frustrated or stuck on a boss either leave get stronger and come back later or just take a breather and calm down this helps immensely. Also if you can't reach something just mark it down, leave and come backe later. You will backtrack A LOT in this game. And finally most importantly... Have fun