If it's hosted in Germany, send the host an Abmahnung by registered mail. It's a cease and desist letter, German style. Copyright law in Germany leaves no doubt about this being very illegal. I'm surprised that they didn't react.

At the same time, file a DMCA notice with search engines. This could get them delisted.

Don't forget to document everything, as you will need it to do the above.

My website (see profile) has a list of English-speaking lawyers in Berlin.