Your Pi-hole is hosted on 192.168.178.7.
Your nslookup via that IP shows that Pi-hole provides the expected replies - if it is queried, that is.
Your client is using your router's IPv6 address instead, i.e. your router is advertising its own IPv6 as DNS server, allowing clients to by-pass Pi-hole.
As your router is of a Fritzbox variety, you can configure it to stop doing so, e.g. Unresolved ipv6 adress in my top list - #4 by Bucking_Horn.