This happens when trying to mirror the URLs listed in my 
first message:

<https://www.naturgarten.org/impressum/infobrief.php>
<https://www.naturgarten.org/impressum/beitrittserklaerung.ph>
p

I start mirroring the site from
<http://www.naturgarten.org/>

After downloading the pages, those two URLs cannot be 
accessed locally. A page is shown saying that there is a 
redirect, redirecting (refreshing) to the very same page, o 
I get an endless redirect instead of the original page!