Route over VLAN and VPN with different distance

Hi,

I've got this situation:

• office 1 (Sophos XG125):
  • WAN1 Internet from the WiFi bridge
  • VLAN 15 on the WAN1 port
  • WAN2 Internet from VDSL (backup)
• office 2 (Sophos XG125):
  • WAN1 VDSL
  • WAN2 Internet from the WiFi bridge (backup)
  • VLAN 15 on the WAN2 port
• office 3:
  • Internet provider Router connected to the WiFi bridge

I've established a SSL VPN (site to site) between office 1 and office 2 that works fine.

I would prefer the triffic between the 2 offices to go through the wifi bridge instead of the VPN and use the VPN as a failover.

How to I accomplish this? I don't see the route automatically added by the VPN.

Thanks!