Branch AD server configuration.

My client is opening a new branch office which requires an AD server configured on-site. Their present domain controller is in a different location and runs DC, AD, DNS, DHCP. I am installing a new server in their branch office which will operate as domain controller with active directory. DHCP is taken care of by another device. I need someone to configure the new server, Windows 2019, which is running on Hyper-V to connect to the original domain controller and replicate logins, GPOs etc. Original domain controller is behind a Sophos XG firewall which I have access to configure, but new office is under the control of a different network manager and only appears to use a standard FibreTo Premises router/firewall.