It seems when I want to add a language to a site, it is per page only. For instance, when I want to add German as a language, I prepare the site as per http://doc.silverstripe.org/sapphire/en/topics/translation and add to my config file:
Translatable::set_allowed_locales(array( 'en_US', 'de_DE ) );
This works: when I add a language to the home page via the Translations tab, I can make a German page appear. But when I look at the page in a browser, all navigation is gone, because all other pages in the site didn't have any language added yet. Is there a way to make all pages accessible in the site, even when no other languages are added to these pages? In other words, I would be able to navigate through the site and see the default English pages when no other language has been added to the respective pages? Or do I have to add a language to every page manually in order to make them visible?