Hello there ,
I installed PPTP VPN server with my microtic router. my users can connect to my vpn network from different regions via windows computers. When my users connect to my PPTP network, they use my internet traffic. I just want them to use it to access my network. I want them to use their internet connections.
Is this possible?
I can do this in openvpn. I didn't see such a setting for PPTP

It's a client-side option, in Windows it's called something like "use gateway of remote network" and it's in VPN's IPv4 settings. Of course you can motivate users to find it, if you disable forwarding from VPN clients to internet (using firewall filter).