RES UTM - XG No access

Hi All

I have the following setup:

XG Firewall as RED Server with two local Networks 10.10.0.0/24 as LAN BER and 192.1683.10.0/24 as Management

UTM Firewall as RED Client with one local Network 10.0.0.0/23 as LAN WIC

XG RED Interface has 192.168.100.251

UTM RED Interface has 192.168.100.254 

The RED Tunnel is up and green.

Ping between the two RED interfaces works fine

The Ping to the XG Firewall IP's (10.10.0.251, 192.168.10.251) works as well.

But I'm not able to access the remote network.

I add static Routes on the XG Network 10.0.0.0/255.255.254.0 -> Gateway 192.168.100.254

and on the UTM 10.10.0.0/24 -> Gateway 192.168.100.251 and 192.168.10.0/24 -> Gateway 192.168.100.251

As well as Firewall rules 

XG: RED,LAN -> ANY ->RED, LAN

UTM: 10.10.0.0/24,192.168.10.0/24, 10.0.0.0/23 -> ANY ->10.10.0.0/24,192.168.10.0/24, 10.0.0.0/23 Action: Allow

But here I have a question, is it correct that on the XG nowhere the remote network (10.0.0.0/23) is needed? 

Thanks for your support!

Best wishes 

Simon