Setting up language breaks the website - how to solve?

Dear community,

from the moment i Add folowing to config.php (like in official documentation)

c::set('languages', array(
'code'    => 'en',
'name'    => 'English',
'default' => true,
'locale'  => 'en_US',
'url'     => '/',
'code'    => 'de',
'name'    => 'Deutsch',
'locale'  => 'de_DE',
'url'     => '/de',

the website instantly breaks.

Important: the website is in a subfolder

and is working perfectly fine (until I do something like above). I tried adding

c::set('url', '');

above in config but it didn’t worked.

I’d be very happy to read how other people solved this.

What exactly is the error message? Did you rename your content files?

thanks. Somehow I missed that crucial step to rename files facepalm!