Andreas,
Facebook Page Tabs don't have the option to use direct links to interior content on your page. If there's one specific page you want the Page Tab to open to when clicked, you can configure the Page Tab URL and Secure Page Tab URL's in the Autotune configuration area to go directly to that link. By default, JFBConnect will set those values to your home page, which is what you see there.
Another option is to use the Facebook Canvas area, which is a way to view your entire site within Facebook. With that, you can deep-link to any interior page you want, like:
https://apps.facebook.com/977710015572577/component/k2/item/26-das-kronjuwel-unter-den-atemreglern-wurde-veredelt
That link actually works if you copy/paste it.
However, the Canvas area is not associated with your Page Tab, so you won't have Like buttons and such for the Facebook Page.
I hope that helps explain a few options, but if you have any questions, just let us know.
Thanks,
Alex