How to setup dns for multiple subdomains

Hello I am trying to create a website in multiple languages. Every language has it own virtual subdomain. So for example here are some urls: nl.foo.eu, fr.foo.eu, de.foo.eu

My domain that generates all the content is foo.eu, it generates the content and translates it to the right language.

This is done with wordpress and the plugin qTranslate-X.

But everytime when I go to an url like nl.foo.eu the page returns an internal server error 500.

So my question is: Do i need to configure something in my DNS to make this possible?

And could I be doing something else wrong?