I have an internet service of 1000 mbps with ISP router SAGEMCOM TG1652A with 5 ports 1gb; If I connect the Google router in one of the ports the port changes to 100mbps; and the mesh internet speed is only 100mbps; If I connect my laptop directly to one of the router ports I can get the 1gb internet speed; is Anything that needs to be change in the router configuration or the google mesh router configuration to have it working with 1000mbps?
Have you tried with a different ethernet cable? From past threads Nest Wifi seems to be a bit finicky about ethernet cables, where a softer, more bendable cat5e has given gigabit/1000mbps, while a stiffer shielded cat6a has capped it at fast/100mbps.
There are no settings in Nest Wifi to control ethernet port speed, so that must eventually be on the other side of the cable.
It also sounds like you are running double NAT, which is not ideal/ recommended. Have a read on these resources: