create vpn bridge to share devices between office and client

hi all, I would like create a vpn bridge and vpn server to create a connection between client devices and my office. It is not easy to explain so I create a scheme in attachmente. Have someone any idea to help me to guarantee connection and the devices connected to hotspot couldn't have any port forwarding but it must create a connection between client and my office. it could be a raspberry with wifi connected to internet and eth0 cable connected to client devices.

Many thanks in advance