Whole Site Down & Inaccessible

Hi,

I don’t really understand computer-speak, but my site (damecacao.com) has been down for over a week, and I’m getting a massive headache trying to understand what I need to do in order to get it accessible to the public & myself again, without losing any of my data. I keep getting the message: “Fatal error: Can’t use function return value in write context in /home4/kegandy/public_html/wp-content/themes/auberge/includes/setup/setup.php on line 806”

By now I’ve wasted hours of writing and updating time trying to make it work, but I cannot figure out how to back up my site onto my computer without being able to actually access the site. Please help!!