Download Google Cloud Bucket as a file (zip)
You seem to be confused a bit about how Firestore stores data and what Google is suggesting you do.


  What is the problem? You are backing up a bucket inside other bucket.


This is not correct.  Firestore stores its data inside some sort of mostly opaque database format.  If you are copying this out to a GCS bucket, that really is an export into a different storage medium and a different format.

That being said, it's still reasonable that you might want to keep your data backups outside of Google (although GCS has a good SLA).  To do that, after you've exported your Firestore data to a GCS bucket, use the gsutil utility to copy that bucket down:

gsutil cp -r gs://your-bucket-name .