Nat 64 Fortigate 5.0.7

hello If you can help me please, I have a LAN with IPv6 and IPv4 another BUT IPv6 network need my internet quit my wan ipv4 (public IP) On fortigate enable NAT64 and IPv6, configure dns ipv6, when I have set my lan interface with IPv6 fortigate answer me pinging, then set the object ipv6 - then policy NAT64 where I let everything that comes from IPv6 to IPv4 and exit Internet, however not work for me In this case my question is that I include additional settings for my network ipv6 internet leave the ipv4 wan ?? I put a default route to the IPv6 network ?? in that case as armaria route? Thanks and sorry but my English is not very good and I'm using google translator