DC not work once remove DNS 8.8.8.8

I have configured Neth with DC but once i am remove 8.8.8.8 entry from DNS then domain controller connected error on dashboard.

Kindly let me know which ip address need to configured on DNS

What other external DNS servers have you got for DNS resolution?

What address do you put in the address bar when you connect to the admin dashboard? Is it http://<server_ip_address:980 or is it http://domain_name:980?