Delete website – clear website, but how?

Hello, dear friends here;

I want to remove my site, but do not know how I do that. A friend of mine sent me the page created on the host “Strato” – he used my site as a demonstration –> http://www.goldenehaltung.de/wordpress

<– He moved away and I can not reach him – He answered no e-mails and also does not answer the phone. I need my side no longer, I can not change – their profile photo, dates, topics, address … because everything has changed.

Thanks for your help and advice
Alois