You would need to add a traffic shaping rule on the office adding subnet 10.20.1.0/26 and then set prio to high.
And on the dc you would set the same kind of rule but now for the destination subnet 10.10.1.0/26
However this would be for all source subnets. So if it need to be specific between 2 subnet you need to create the rules in a group policy, and apply that gp to the source vlan