Setting up openwrt router as VPN access point


First off all, I know very little about setting up routers and less even about how to set up vpn.
Anyway here's my problem: I'd like to use an Mi router 4c (latest openwrt firmware installed) as an VPN wireless access point. At home, I have my isp router ( sitting behind a running softether server on a rpi4 (, without securenat enabled. Ports are open and everything's working fine, since I can connect to the server using a windows pc with softether client (I even get an ip assigned by my isp router).
At my office, I have another ISP router ( and I would like to use my Mi router 4c as an wireless access point, but offering the possibility to connect some of my devices to the softether server, with ip assigned to them by my router at home.
Is it possible? And if so, could someone please guide me? I just did a fresh openwrt install (nothing configured yet, so default ip is still I also installed softether client, libs and lucy interface).