Can ping DNS Server but can't resolve any name

I have a XG Firewall with an active SSL VPN. I'm now trying out Sophos Connect as an alternative / replacement and so far I was able to connect from my client to the firewall and access the resources as long as I access everything via the IP address. But I can't resolve any name. My Client configuration looks like this:

The DNS Servers are correctly added to my client: 

And I can also ping on the IP 192.168.109.211 successfully.

In my firewall rule I allowed the access for All Services to the internal network.

Do I have to adjust something particular here to make that work?

Thanks

Nino