Access Website hosted by Raspberry Pi using the public IP-Address

I hostet a small website on my Raspberry Pi using apache. In my home network I can access the website by simply entering the IP-Address of the Pi in the URL bar of my browser (e.g. http://192.168.178.104/index.html) I forwarded the port on my router (Fritz!Box) and now I am having trouble accessing the website when I am not in my home network. This is the IPv6 Address of my router: 2001:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx And under the section "Portforwarding" in my router's interface it shows me these addresses for my Pi: 192.168.178.104 and ::818:xxxx:xxxx:xxxx

What I've already tried:
http://[::818:xxxx:xxxx:xxxx]:80/index.html http://[2001:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx::818:xxxx:xxxx:xxxx]:80/index.html http://[2001:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx::192.168.178.104]:80/index.html

But nothing seems to work. Help (and an explanation) is very much appreciated!