There are 2 routers with four Atherous 5213 cards.Two of them are linked point to point in bridge mode with NICs.I want to set up and connect other cards and after that to establish nstreme-dual with all.Is it possible to do that,because i had no success in past 2 days in connecting...?

I'm new to this but I don't see any reason why not. What are you running this on a PC? RouterBoard?, two issues you might have is not enough power to run all the cards and or not enough CPU power to run NStreme with the other link running.

First I want to try make connection between both cards which are not linked now,but i can't.Is there problem if there are other two cards which are already connected?

Power supply - 350W
CPU - Athlon 1200MHz
RAM - 128MB
Mikrotik 2.9.2