Vps single nic publi ip without nat

[ST]

Hi everyone. I installed openvpn for the first time on a single nic vps and public ip address. on the other side I have a mikrotik with the subnet 192.168.2.0/24. on the server I created a dummy interface with ip 192.168.3.100 on which I listen to software. I need the following connections

192.168.3.100 -> 192.168.2.1 (the server registers on the client with the address 192.168.3.100)
(the client replies) 192.168.2.1-> 192.168.3.100.

Do you have an example server.conf file? Thank you