thank you for the answers. I don’t know what happened, but now it works
i tried disabling the plugins. I saw now that i can insert pictures, so the media library seems to work, also after reactivating the plugins. although i cannot get an image to show up in my header or slider. Is that media library related at all? or is it the theme?
Before the update to 3.8 i couldn’t see any pictures in the media library, now I can see the little examples in the library.
