To download one file, open its three-dot action menu and select Download. Your browser saves the original file.
To download a folder or several selected items, select them and choose Download. Files prepares a ZIP archive for the group. The archive is a copy; the originals remain in the Vault.
For a large collection, use the Nextcloud desktop client instead of creating one large browser archive. Synchronization transfers files individually and can continue after a connection interruption.
Files shared with you can be downloaded only when the owner has granted download permission.