Configure Sophos XG With VPN Draytek (Vigor 2915)

Two things:
1. This design is broken.Why use a 192.186.1.0 as your network? This is publicly assigned. You ask for "best" topology: use 192.168.2.0/24 for Site A and 192.168.1.0/24 for Site B.

2. This is a kind of "wash me, but don't make me wet" question/wish: the vigors are your endpoints for the VPN tunnel. So these are the gateways, basta. What you try to do is assymetric, you should avoid this. So to correct this, the vigor in site B has to know a route to the LAN in site A.

What I understood is that the computers inside the internal network must have Vigor IP as a gateway in his network card . that's right?

Thus, all traffic from the internal network, whether in the direction of the VPN tunnel or the Internet, comes out through Vigor and the Internet line connected to it directly, In this case, I will dispense with Sophos

In case all PCs have Vigor Gateway , how configure Sophos to Site B know route to Lan in Site A

You have another Sophos Firewall at Site B?

I do not have it, the Vigor device is directly connected to the Internet

I have Sophos just in Site A

That is problem in site A or site B?? . Do you mean configurations for routing on vigor in site B

Can you show us a typical ip configuration (ip/mask/gw) of a client at site A and the same of site B?

Site A

IP : 192.186.1.40

Mask: 255.255.255.0

GW: 192.186.1.101          (Sophos Lan IP)

Site B

IP : 192.168.1.20

Mask: 255.255.255.0

GW: 192.168.1.100       (Vigor IP)