Multilanguage Site Error

Hello Dear Plugin Developer

The plugin is very easy to use but I have one Problem that I cant find it. I have a Website in 2 languages. The Default language is english and the other one is in german. The Default language page english is translated automatically because I buy the theme and I would like to translate this in german. When I translate strings from english to german and go to the link german I get an error.

Error: http://www.info-9.com/de
Not Found
The requested URL /de was not found on this server.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

Could you please help me and could you say me what I must do to Change the error?

Thanks

The page I need help with: [log in to see the link]