I started the SharePoint Foundation Search Service on the server.
I added the Managed Account.
And I started the SharePoint Foundation Search Refresh.
But I allways got the same message.
Then I looked in the Event Viewer and I found following "SharePoint Foundation Search" Warning (Event ID: 14):
The start address sts4://win-u71mv1i4epi/contentdbid={521dee71-a532-4935-b906-5e9ed5f49d33} cannot be crawled.
Context: Application 'Search_index_file_on_the_search_server', Catalog 'Search'
Details: The object was not found. (0x80041201)
I found this Forum Entry: Search Problem with SharePoint Foundation on SBS 08
And there I found the source of my Problem: It was the alternate access mapping
here what I got in the central administration.
and here what I had in the IIS Manager
So I needed to add on binding and my problem was resolved. Here what it should look like: