@Dj1979 In general there's a procedure to unbind your router from a TP-Link cloud account, before deleting the account - check this solution. If you have already deleted the TP-Link account bound to...

@Thlian You should buy another Deco unit to expand the Deco mesh network. Any Deco unit would do the job. Check this guide before making a choice.

@Fms_muc Now that everything is clear regarding C50 'range-extender' mode bridge type connection, here are the routers that currently support WISP. Only one of these supports 5GHz band - TL-WR902AC....

@Fms_muc Yes, I confirm that C50 in 'range extender mode' does not do NAT - it's a bridge connection. Your friend's TL-WR841N does have 'Hotspot router mode (WISP)', which does what you're describing...

@Fms_muc Actually it does matter. If a device connected to the ISP router receives an IP address in range 10.10.x.x and you have set Ç50 static LAN IP address to 192.168.0.1 it won't work for sure....

@Fms_muc When you connect a device (a mobile, laptop or PC by DHCP) directly to your ISP router, what's the IP address that the device receives and its gateway ?