browser does not open install.php

When did you register this domain name? I can’t find valentin-zahrnt.de at all.

I registered it three days ago and I got the accesss codes yesterday.

Try contacting your hosts about this. It’s definitely a hosting/domain name issue.

And what should appear if I just enter valentin-zahrnt.de (without having installed wordpress)?

Some sort of holding page. The exact page varies from host to host.

Thanks!