Thank you, that did the trick!
Only I have a new problem now. PHP looks suddenly disabled
I get a text file, when I visit: '127.0.0.1/phpmyadmin'
Like this:
http://postimage.org/image/2j6o8olyc/

I already tried to add the line:
fastcgi_index index.php;
and restarting nginx. That didn't work
Rebooting also didn't help

Do you know how I can enable PHP again?