Route all external traffic via site 2 site ipsec

Hi,

I tried to google and to search the forum, but haven't really found a solution...

I have an UTM 9.3 (192.168.2.1) in the US with a stable site 2 site ipsec tunnel to a remote fritz box (192.168.1.101) in Germany. I can reach all devices in the remote network very well.

What I would like to achieve is:

Route traffic to certain external hosts / networks or even all external traffic through the VPN tunnel ("Full Tunnel").

I followed the how-to https://www.sophos.com/en-us/support/knowledgebase/115661.aspx, but with no success.

I also tried a policy route: Gateway Route, Source Interface: internal, Source Network: internal network, Service: any, Destination Network: External Network, Gateway: fritz box (192.168.1.101).

In my findings the configuration on the fritz box side should not cause the issues so far, since traffic is not even directed to the tunnel so far. (Or are some crucial routes negotiated in the background already, when the tunnel is established?)

Any tips / recommendations would be appreciated. :)