VNC Firewall and NAT rules?

Hi,

I'm trying to connect to my Mac with RealVNC on port 5900 (VNC)
But the connection always times out.

I tried so many settings, but i just deleted them all because it was still not working. :confused:

Can anyone tell me which settings i need to get VNC to work?
I tried to find it on this forum, but that's not working.

I want to be able to connect to my Mac (RealVNC) from outside my network, but also from the internal network. I'm testing from inside my network now.

I got a new installation with Sophos UTM 9

eth0
Internal
Ethernet

eth1
External (WAN)
Cable Modem

I also got double NAT, my cable modem is a router. And i cant switch it off. (Cable company settings) But i forwarded all ports and DZM on my modem is set to the external IP from the Astaro. These settings should be ok.

Can anyone help me with this?

Thanks :-)