Pi-hole is a Linux network-level advertisement and Internet tracker blocking application which acts as a DNS sinkhole and optionally a DHCP server, intended for use on a private network.
Install the App Store
I would change the WEBPASSWORD environment variable.
You can check if port 53 is clear with running:
bash -c "$(wget -qLO - https://raw.githubusercontent.com/bigbeartechworld/big-bear-scripts/master/disable-dns-service/disable_dns_service.sh)"