IPv6 Connections works not properly

No - Did the check right now again.
Diagnosis gives me:

  • Global IP: 2a02:810c:880:68e4:e005:eb17:31d5:4708
  • Local IP: fe80::29a3:717f:52d0:4be7
    Fritt Box:
    2a02:810c:880:68e4:97c9:6186:2884:67bd

Can you explain me what is the IPv6 Interface ID?
In my case: