According to your gallery's 'config.xml' file, the first image in your gallery should be located here: http://eye.de/gal-html5/marilena/images … _1000h.jpg
... but going directly to that location in a browser results in an error 403 (forbidden).

Please check that your thumbnail and image files have been uploaded to the correct locations on your web server and that their permissions (and the permissions of the 'thumbs' and 'images' folders themselves) are not too restrictive.
Default permissions of 755 for folders and 644 for files should be fine.

You can check and change permissions with an FTP program such as Filezilla or via your web hosting account's online file manager.

Also, please see this FAQ which may help:
My images show locally, but not when I upload them to my website. Why?