WAN port on box???

Hello everyone,

I have a question that seems to have been touched on before, but I'm not quite sure, as I don't clearly understand the answers given.

So, my father works at Veolia, and he finds all sorts of things in the trash. A few weeks ago, he found an SFR box in some bins, complete with everything inside: HDMI cable, RJ45 cable, remote control, etc. ... even the batteries.

Old school, my father doesn't even have internet at home, so he can't test anything, but he thought of me and said, "Remember that RJ45 cable that runs from the ground floor to the workshop (15m of Cat6 RJ45 that goes up a floor and passes through 3 walls 90cm thick, the Wi-Fi doesn't reach that far)."

We were thinking of connecting the SFR box to the WAN port (which is RJ45), and on the other side connecting it to one of the RJ45 ports, thinking that my original ISP's box would provide internet to the SFR box, which would then re-emits it via its Wi-Fi, like a Wi-Fi powerline adapter...

Let me know if there's anything feasible here if you have any ideas? I would be curious to see if we could "recondition" a box this way.

I'm available if you have any questions.

Thank you in advance to everyone for taking the time to read these few lines.