Hey Jan,

To proceed with troubleshooting your issue, I would need your backend and ftp access.
For backend access it seems there is another layer of user and password I have to get through before reaching your backend login (refer screenshot)

As for your ftp, I am getting 'Authentication Failed' message. Perhaps you can recheck the access of both backend and ftp then update those login information in http://stackideas.com/dashboard/site
After that, let us know and we will continue the troubleshooting process, thanks.