wrong domain suffies for clients

all clients at pihole show up with a wrong domain suffix.
My setup:
settings via a DHCP server (Windows), it gives out three DNS servers in this order:
Pihole
Windows Server
Router (fritz.box)

In Pihole settings under conditional forwarding, I have this set:
172.21.44.0/24 172.21.44.12 (Windows Server) local.domain

When I ping a network client from my client, it resolves with local.domain
When I do a nslookup, pihole answers with the fritz.box suffix.
However on the pihole all clients show up with fritz.box suffix, and some with wrong host names. It looks like it doesn't aks the Windows server but instead only the fritz.box
There's also a DNS server running on the Windows Server

Please upload a debug log and post just the token URL that is generated after the log is uploaded by running the following command from the Pi-hole host terminal:

pihole -d

or do it through the Web interface:

Tools > Generate Debug Log

I solved the problem by making Pihole the DHCP server