Error after opening page from Panel

i tried to open a page, that is listed in the panel. The panel works fine, but i can’t see the content, just the Error message ( This page is currently offline due to an unexpected error. We are very sorry for the inconvenience and will fix it as soon as possible. Advice for developers and administrators:
Enable debug mode to get further information about the error.) . The console is giving me this essage: Failed to load resource: the server responded with a status of 500 (Internal Server Error)
I’m using XAMPP and Chrome. What could be the problem?
Thanks in advance!

Please enable debugging in your config: (although it should be enabled by default in a starterkit).

Maybe a weird question but in which file?
tried it in the console but got a “illegal return statement” warning.

In site/config/config.php, within the existing return statement.

I see: there was no config-folder. Added it from the starterkit and know it works. Thanks a lot!