By default, SSH on Ubuntu comes configured in a way that disables the root users log in. This was originally enabled as a security precaution which means that you cannot directly log in as the root user over SSH. However, you can usually get around the need for root ssh login by using the sudo command. In some cases, though it’s just more convenient to get directly logged in as root.
The most important thing you can do to protect your server against data loss is to take regular backups. Properly configured backups are a critical aspect to the maintenance of any website and can mean the difference between a quick recovery and rebuilding a site from scratch. If a critical file were to be deleted accidentally, a database became irreparably corrupted, or your site was infected with malware, would you be able to restore your data and get your site back up within a few minutes?
If you can’t answer “yes” to these questions, then it’s time to review your backup strategy.