Separate VPN PPTP networks

Hi
I would like to use RB951UI-2HnD as a VPN server for several separate VPN PPTP networks.

Each VPN network consists of client 1 and several other clients that needs to connect to client 1 local network (172.16.17.xx)

All the external sites connect to my router with VPN server (constat and public IP)

How to separate the VPN networks from each oder and from local (mikrotik ruter LAN) ?
below drawing of the situation:
Konfig VPN.png
Regards
Artur