take your time don't worry. You are one of the few Naruto stories where the character has real development. And then the mastery of water is super original! No pressure, rest and don't force yourself to do lots of chapters if you want to be calm
The way I write is with a outline and I just fill in the blanks. Not even trying to stay true to what is on the paper and using some hard plot pushes to get in back on track when needed lol
If he ever gets a summoning contract, it should be with cats or axolotls. Cause cats are like water, in many ways. While axolotls are the dragons of the sea.
I've heard from an artist on YouTube (Ronillust) that a blank page can be intimidating, so it can be good to first fill a piece of it with something unimportant before proceeding.
Either way we have time, no pression.