That's why I want to use my Google Drive as default data directory meaning that all the course material goes as default to Google Drive. How can I do that? Obviously Moodle has to have full access to this Drive, but I have no idea where to start with this.
So normally when someone uploads material into Moodle, it goes to place which in File Picker is called "Server files", as you can see from attached picture. I want this "Server file" to be located in Google Drive and not on my own Moodle server. How can I do this?

Hi,
I would be interested in this way of storage. If you get any update or workaround, could you share, please?
Regards
Please see:
https://docs.moodle.org/38/en/Google_Drive_repository
I see you have a 'Google Drive' in your screen shot.
It's a repository which is different than entire moodledata - which is for all users on the moodle server. Its the apache service that has access to moodledata via moodle php scripts.
Please see https://cloud.google.com/storage/docs/json_api/v1/buckets
While you can mount a google bucket and name a folder there, using it for moodle's caching or moodle's filedir (where the files uploaded to moodle are stored) there is no 'web service' user (such as the one your moodle runs under - example: apache or www-data) with the bucket. A GB is tied to a google service account and not sure one could ever get user ownerships/permissions to work.
A GD repo does require all users to have a Google Account (or gmail.com) and if a Google 4 Edu set up would involve the Google Admin for domain to attempt set up a Google OU - no interface in Moodle admin to do that.
Not discouraging you from trying, however.
'SoS', Ken