leewhat

Is there ethernet port/cable or coax on the other side?

Gateway 192.168.0.1?

Why is dns 192.168.1.1?

Try readjust the other Deco location, you can't put too far if its wireless backhaul.

It does if you enable the share in router. Can check the tutorial here https://www.youtube.com/watch?v=Q2sLtVdZ5fI

like hamachi?

No, Access Point would extend the connection from initial router.

it will be compatible, run at 1Gbps

Set the new router as Access Point mode, plug the ethernet to LAN port, not WAN.

seems can go more than 2.5Gbps https://redd.it/121sxom

Could be ethernet cable issue since ethernet stuck at 99Mbps. Unless your PC has 100Mbps network card?

Do you have Public IP or Private IP (CGNAT) from ISP?

You could use Tailscale if you don't want to pay that Public IP monthly fee.