I'm new in PWA and want to create PWA and React to create Android and iOS apps. I only have the REST APIs (including login with username and password). I would like to create an app with login and display my pages in the menu on the left side. Could you suggest a Doc or GitLab source where I can start?
You can create your normal React project complete with the features and functionality you intend to have then convert into a PWA after that.
To add PWA functionality into a plain React project, you can follow the steps outlined here
To add PWA functionality to a Next JS project, I would recommend making use of this package. Here is an article that walks you through how to achieve that.
You can publish your PWAs to Play store and App store, read more here