Also a big Thank to Tony for his immediately help and correct answer. Thank you Tony.

@Tony Thanks for everyone for the answers. Finally late the morning i found the solution. I read somewhere in web that if someone have a router/modem and wish to connect an external router for any...

First i connected my CYTA ( Cyprus) router with the Archer C7 by ethernet !! LAN 1 with LAN1 of Archer C7. I have internet connection with my C7 TP LINK. Also Ethernet connection is fine....