Forward IPv6 from WAN to Server with IPv4
Solution 1:
I got my Problem solved, however i had to switch IPv6 for this. I used this tutorial as a help: https://blog.veloc1ty.de/2015/08/22/pfsense-ipv6-delegation-hinter-fritzbox/
Basicly i had to configure my Fritzbox to allow secondary routers and give them a Prefix < 64 Bit (I used the IA_PD and IA_NA Method).
Then i configured the Gateway like shown in the turoial with 60 bits. After that i just needed to create a Firewall Rule for Port 443.
On the Clients a added iface eth0 inet6 dhcp
to the /etc/network/interface