files dont get loaded anymore

Hello,
we tried hummingbird for optimizing our page.

We moved some css files to the footer and recognized the site is not working anymore.
We unchecked the “move to footer” button, deactivated and then deinstalled the plugin.

Poorly the files are absolutly not loading anymore.
How can we get our site back to the state before hummingbird?

Thank you for your help!