404 Everywhere - Content not accessable

I run a Multisite with the wpmudev theme bpdaily. Link
Something happened! If I click on content or on subpages there is nothing (404), only my Home page is still active. I even cant access the subpage dashboard!

I backuped my page, but nothing changed!! (the content is not deleted i checked it in the backend)

Do you know what can cause this? If the backup didnt change it, maybe something in the database?!

please help, Kev