First, don't panic...these things happen in Internet.
The good news is we keep backups every day so most probably restoring the last good backup will bring back your site online.
If the hacker put a text to contact him/them to have your site fixed or recovered, please do not do that, most probably the only thing you will do is lose money, instead contact us immediately.
The bad news is, if you was hacked is because you had a very poor login credentials in your hosting panel, script administration panel, etc. or you had an outdated script and someone used it to gain access to your hosting account and files.
Please note although we could restore your files from our backups this do not means you are safe, once restored you have to audit your files, change your passwords and update any script or plugin (like wordpress plugins, etc) you may have in your account.
Do not try to correct the hacked files, based in our large experience any hacked account that is attempted to correct is hacked again, as hackers always leave backdoors or other scripts to gain access again in the same account. The best way is restore the files from backup and then find and close the security hole.
Some of the cause of a hacking could be outdated scripts or the script themes and plugins, weak login credentials, disclosed credentials, etc.
Also note we are not responsible of your site and scripts maintenance, we keep our servers secure and safe but each user have to keep they account, scripts and credentials safe and in good standing. Is not our responsibility investigate the origin of the hack in your account, if you are interested on it let us know and we could have a paid security professional available for you. Any restoration or additional work could be charged.