Overview: we have provided you with a private VPN (PWAN), but you want to connect a Windows PC and still have normal Internet access on the PC whilst allowing you to access devices and resources on the VPN LAN. Here's how to enable that.
Prerequisites: You must first create your VPN connection in Windows 10. See the official Microsoft article "Connect to a VPN in Windows 10" https://support.microsoft.com/en-us/windows/connect-to-a-vpn-in-windows-10-3d29aeb1-f497-f6b7-7633-115722c1009c
Navigate to: Control Panel\Network and Internet\Network and Sharing Centre
Click the connection name hyperlink
Double-click "Internet Protocol Version 4 (TCP/IP)"
Disable "Use default gateway..."
[OK], [OK], [OK]
Disconnect and reconnect the VPN.
Now Windows uses your existing Internet connection as the default gateway, but still "understands" that a route exists to your 172.16.xxx.xxx private LAN across the VPN.