updating text of a mobile app (newbie)

[Nicolas Cueto]

A goal this year is to get an app (for foreign language learning) on the
Android and iOS stores. To this end, I have begun to re-study LC8's app
building course; LC itself I've been using for decades.

Let's say my original app gets approved. In that app is a datagrid object
list consisting of 10 vocabulary categories, the contents of  which are
read in from a text file in specialFolderPath("documents"). A few months
later, however, I discover more vocabulary categories are needed.

What do I do? Can I somehow "download" a new text file into
specialFolderPath("documents")? Do I have to completely update my app? Or
something else?

In the past what I've done for my desktop Windows standalones is to
download data from my webserver over the internet. But, I imagine mobile
apps must work differently.

Hand holding very much welcome!

--
Nicolas Cueto