I would like to know if my approach is correct. I have an ISP->Router and to router 2 servers are connected (Windows and VPN) and a switch with local computers. People from outside should connect and use my local computers using VPN, is that correctly shown? Also what I mean, when they reach the VPN server, will be able to use the LAN as if they were there - I hope.
In this drawing, all your network is behind your FW so you just have to allow traffic from external clients to VPN server in port 443 (or whatever). When an external client get a local IP, it's in your interal network. Since you have a router from VPN server to local computers, be sure about routing between VPN IP pool and local clientes network.
Tip: A more secure approach it's to connect your VPN to the FW and create two zones. A DMZ zone for VPN server and trust zone por internal clients. Read a manual from major vendors looking for typical deployment scenarios.