Swift and Firebase error. Cannot find 'firebase' in scope

Here are some stuff you can do to solve this error message: Cannot find 'firebase' in scope.

Firstly, check if that solution works for you: https://github.com/firebase/firebase-ios-sdk/issues/6066#issuecomment-662580211

If not, check if you're importing the right library to work with firebase and swift. Take a look in my code and see if your is the same:

import FirebaseFirestore

...

private var db = Firestore.firestore()