After Installation only Ngix page

I just installed Zammad on Ubuntu 18.04.
Zammad is running, all 4 Services are up.
opening the site “localhost” or also from other machine with the ip-adress, it shows only the standard Ngix-welcome page. Not a page from Zammad.
What could be the problem for this?
In zammad.conf the servername is “zammadsrv”. but on this, nothing is reachable.
Thank you for any help!

maybe some problem with postgresql, on running postinstallscript, I’ve got this error:

/opt/zammad/vendor/bundle/ruby/2.5.0/gems/pg-0.21.0/lib/pg.rb:56:in `initialize’: could not connect to server: No such file or directory (PG::ConnectionBad)
Is the server running locally and accepting
connections on Unix domain socket “/var/run/postgresql/.s.PGSQL.5432”?

But Postgresql is running…???

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