Word is generally not a good choice for composing text; I'd recommend using something like emacs or vim if you're on N*X platform (Mac OS X, Linux, Unix) or Notepad++ if you're on Windows.
Word is what is called a 'word processor', it's designed for laying out and formatting text, whereas the other are 'text editors', designed for editing text.
Personally I would reccomend familiarizing yourself with Markdown, a widely used plain text markup language (it's what's reddit uses for comments and posts, more or less).
The bits you need for writing this kind of stories is really simple as well. :)
## Chapter Name
A paragraph long establishing text.
"Some dialogue." a character says. "And then some more, maybe?"
Another paragraph.
I hope it's not breaking any rules, but the final version of this story can be found here:
https://www.amazon.com/gp/product/B07J4K4SCC/ref=dbs_a_def_rwt_hsch_vapi_tkin_p20_i0
I'll try to clear my current workload and visit these girls again. I bet they're having a lot of fun...