@Faucon-Ngando he's using a docker-compose file to run both a postgres sql container and mango container inside a single network.
The volume property maps the directories inside the docker images to real directories on the host system.
For exporting you'll need to do a sql backup and a complete nosql backup (if applicable)
These outputs should appear inside you /opt/mango-data/backups directory.
If you're not using an external sql you should still be able to run using the same configs in that docker-compose file, minus the postgres related entry as all of your data and backups should exist in the mango-data directory...
Fox