This game is easy only took me 2 tries because the 1st try I forgot to press Y to continue. All you have to do is go inside him or stay on his head and shoot him from there . The last part with the beams and the eel is the only reason why you should be on his head !
The last boss is so easy, all you have to do is doge the fireball and whenever he is about to move to the left or the middle or right sides just hit him with your sword it takes patience