Name resolution from the server network for Openvpn clients

[TOM99]

Hello

I have some Opnvpn SSL clients that
- can connect correctly
- have access to the internal network
- can resolve the names in the server network

But the clients on the internal server network cannot resolve the Openvpn client names.

Ping and access via the IP of the VPN client work

the IP addresses are displayed correctly in the connection status on the firewall

VPN clients do not register on the DNS server in the network, although he is specified.

How can I ensure that
- the clients register in the Server- DNS
- or the firewall does the name resolution, it must have all the information

Greetings
TOM