"how can i change that text without updating the app, kinda online i guess."
normally there is no way. You cannot change without reupploading file. I faced the same problem in my app, and found solution.
1. I made a secret admin login to app, and then I made a text object as a textbox object in admin mode.
I used "Firebase" plugin to store text online, and in admin mode I can change it inside app, and everybody will see changes, because text is always taken from "Firebase".
Or you can use MYSQL plugin, and store data in MYSQL, but Firebase much easier. Hope I showed you the way to move.