Interact a watch app and a companion Android app

I developed an app for the Garmin watch ( vivoactive 4 and 4s) I want to store the data in the firestore through an Android app. How should I do that? Is there any video tutorial that I can use? Can I store it directly in the fire store? If not, how should I connect the watch app and the Android app? I have read this link https://developer.garmin.com/connect-iq/core-topics/mobile-sdk-for-android/  But it's very abstract and without details. I'm kind of a beginner. I would a appreciate if you can give me an example code or a video tutorial for that