My problem is theme related, I think. Or a plugin which I use in the design (frontpage slideshow) is bugged after I upgraded.
First, I only got blank pages (no text, no design).
Then I renamed the plugin folder. Now some of the page showed.
Then I updated all plugins and activated them again
Now I have parts of the page, but no articles. Pages work fine. I think it has to do with the frontpage slideshow which I have only on the front page with the news and not on pages.
Everything works fine with the standard theme.