So I added 'redirect-gateway def1' to client config to route all traffic to openvpn server. then my connection to internet completely goes out and for example browser says can not display page.
you can:
1) Enable NAT on traffic coming from openvpns server tun interface destined to internet on your windows server (maybe via RRAS)
2) Setup a proxy service on your windows server then use it from your client.
Michael.