[initial steps]
Navigate to functions directory.
install firebase CLI (to use npm install node js)
npm install -g firebase-tools
install dependencies
npm install
login to firebase
firebase login
firebase init
Do not overwrite package.json
Deploy your Cloud Function for Firebase with
firebase deploy --only functions:dialogflowFirebaseFulfillment
Source: https://firebase.google.com/docs/cli/#setup
Database used: cloud firestore https://firebase.google.com/docs/firestore