This illustrates what my ISP offered to me. Sorry about the language, if needed I will try to translate.
In short, I got assigned an external ipv6 address, /64 subnet, "connecting segment" (the /126 thing) and I have received default gateway.
In order to make it work I need to manually add a ipv6 neighbour which is actually an isp router (default gateway) which I can do with ndp -s [ipv6] [mac]. After that I can ping the gateway (otherwise I get an error) but test-ipv6 still doesn't see my ipv6 address (pinging google on ipv6 also times out).
I use separate subnets for lan and wifi, but I only enabled ipv6 for lan subnet (until I get a /56 subnet), in dhcp server I set RA to unmanaged for lan and Router only on lan dhcp is disabled and RA set to Router only. I laso added firewall rules for ipv6 traffic.
Any help appreciated...