Complex sentence: Ponyo and her father have a confrontation, where Ponyo refuses to let her father call her "Brünnhilde" and declares she is Ponyo, and voices her desire to become human, because she has started to fall in love with Sōsuke.
Split into simpler sentences: Ponyo and her father have a confrontation, where Ponyo refuses to let her father call her "Brunhilda". She declares her name to be Ponyo, and voices her desire to become human because she has started to fall in love with Sōsuke.