Arduino client to a router with page authentification using ethernet shield

So basically , what I'm trying to do is to connect my arduino mkr to a router using the ethernet shield . But the problem is that : if I want to connect to the router with my laptop using an ethernet wire , I'm redirected to an authentification page where I'm supposed to write my login and password . So it makes connecting the arduino to that router way more difficult .
My problem looks like this one https://forum.arduino.cc/index.php?topic=306900.0 , so I guess I have to add An http authentification request but It's still not clear .
If somone can help me it would be really really appreciated .
Thanks .

My problem looks like this one https://forum.arduino.cc/index.php?topic=306900.0 , so I guess I have to add An http authentification request but It's still not clear .

No, if your description of the login procedure is correct, you have to send the credentials to the target of the login form page you get on the computer, extract the returned cookie information and send that authentication cookie information in every request you do afterwards to the standard API.
The exact way to do this depends on the actual way your router handles this. And keep in mind, if your router gets a firmware update you might have to start over again if they change the login procedure.