Access to multiple remotennetworks via single site to site connection

Hi everybody

Im im new to the Astaro router and have run in to a small challenge regarding site to site connections and visibility af remote network.

Im having trouble connecting to multible remote networks via one single site to site connection.

My setup is like this.

Im placed behind router C.

I have at site to site connection to router A(Draytek) and can see the network behind router A.

Router A connects to router B thru another site to site connection but im not able to see the network behind router B.

I have tried to place the network behind router B in my site to site setup under remote networks in the remote gateways setup just as i have done with the network behind router A.

I would like to be able to connect to the network behind router B via my site to site connecion from router C to router A.

Router A and B are from DrayTEK
Router C is a ASG :)

Any suggestions ?

Best regards

sej75