In addition to FTP and SSH, you can also use SFTP at Site.eu. This is very similar to FTP, but is more secure and uses the SSH connection.
First you need to enable and configure SSH. Check out the other article on this: Information about using SSH
After that, logging into SFTP is very easy. Use your DirectAdmin username and as your SFTP address use the URL of your DirectAdmin control panel, but with "sftp://" instead of "http://" and without ":2222". So suppose you are logged in to "https://da005.site.eu:2222/", then your SFTP address is "sftp://da005.site.eu". You can also use your own domain name as your SFTP address by putting "sftp://" in front of it, but then your domain name must already point to your web hosting.
Do you use Filezilla to connect to SFTP? Then make sure you select the correct SSH key in your profile to log into SFTP.
From the command line, if your web hosting server is "da005.site.eu" you can log in like this: "sftp email@example.com".