npm install -g firebase-tools
firebase login
Use the same email that you use for Dialogflow!
firebase list
firebase use --add
select your project
cd functions/
npm install
When done editing :
firebase deploy --only functions:dialogflowFirebaseFulfillment
Go to https://console.firebase.google.com/
Enable cloudfirestore database (use testmode = no permission restrictions)
https://console.dialogflow.com/
https://console.firebase.google.com/
https://dialogflow.com/docs/reference/fulfillment-library/webhook-client#webhookclient