Google Cloud Functions: Project layout for Github

I'm starting with Google Cloud Functions, and I want to use a real editor + github instead of the inline editor.

For an existing Google App Engine Flex(php) project, I've modified it so that it publish on PubSub some data about user.

I want to write a set of functions :

One function that update BigQuery, and post on a topic that a user data has been updated
Subscribed to this update : Several functions would run on query on BigQueries and store the result in Firebase (for a mobile app to display the data statistics)

Here are some basic questions I couldn't find any answer :

How can I organise my project? What is the expected layout so that GCP can fetch the project from github and run it ?
[Optional] Can I have multiple file for one function to organise my code ?

I've found this : https://github.com/PrinceCornNM/generator-firebase-cloud-functions but I also read that the Function for firebase was somehow incompatible on a stackoverflow post.

Here is how I made it work :

Setup the Github Repository

Create a repo on Githup, checkout from my IDE
Create a folder with the name of the function 'processNewTroncQueteur'
Create a package.json and index.js in this folder, and copy the content of my working function from Google Cloud Function
Commit

Check my repository as an example : https://github.com/dev-mansonthomas/RedCrossQuestCloudFunctions

Sync my Github Repo with Google Source Control

Go to https://source.cloud.google.com/
"New Repository", "Connect external repository"
Select your GCP Project, then choose github, check the checkbox for consent, and click "Connect to GitHub" (follow instructions)
Choose the project on GitHub, and click "Connect Selected Repository"

(I had to try twice, the first time I got an error without details)

Create your Cloud Function from Source Control

Go to https://console.cloud.google.com/functions/
New Function
Choose Name, Memory, Trigger, Runtime, and region (advanced)
Choose "Cloud Source Repository" for "Source Code"
Repository : Copy/Paste the repo name from "Google Cloud Repository", you can find it, in the upper left corner of the screen, when you're in the repo. For me it's: github_dev-mansonthomas_RedCrossQuestCloudFunctions
I used, Branch/Master
Directory with source code : the name of the folder 'processNewTroncQueteur'
function to execute: 'processNewTroncQueteur'
Create, and I've tested it and it works.