TypeError: database.collection(...).set is not a function at onFinish
db.collection("users") returns an object of CollectionReference. CollectionReference has no function 'set', Hence the error. Perhaps you are looking for the function 'add' which adds documents.
Replace
db.collection("users").set({
points: 0,
CurrentLevel: 0
})
with
db.collection("users").add({
points: 0,
CurrentLevel: 0
})
And I think that should solve your problem