I look for this article:

https://www.heise.de/ratgeber/Anleitung-fuer-einen-Eigenbau-Waermetauscher-fuer-das-Taupunkt-Lueftungssystem-7183776.html

, and it seems to be on archive.is, but not really. The zip file can’t be downloaded, and the article frame never comes alive.

Is this content available? If so, where?

If the content WAS on archive.is, why is it gone?