Your question is quite vague, but I think I've worked out what you're trying to ask.
The problem is that your VPN is configured to set itself as the default route for the client computer so all traffic goes through the VPN. This is sometimes exactly what one wants, but what you appear to want instead is only for
some traffic to go through the VPN, letting everything else use the old default route to the local Internet connection.
The solution may be as simple as "
add-default-route=no," but your client VPN configuration can play into this.
Once you do this, you may then need to add a more restrictive static route, like 192.168.88.0/24 pointing back to the VPN connection so connections to only those addresses go through the VPN. How you do this depends on details of how the VPN is set up. If the IP address of the client comes from a DHCP server running on the MT router, setting a
classless route is one way to solve this.
If that doesn't work for you, we need more details about how you've set the VPN up. Send the "/export" info stripped of sensitive info, what VPN client you're using, configuration details for that client, and so forth.