Redmi Note 8 Pro and Miracast, does it work for you?

Question

Android

Hello everyone, I bought a Redmi Note 8 Pro phone and ran into a problem. Everyone is silent on w3bsit3-dns.com, so I wanted to ask if anyone checked Miracast's work? I have such a situation, the Internet works via wifi at 2.4GHz (there is no other router available), a 4K Samsung TV is connected to it. As soon as I press the Cast button in the blind and select the TV, the Internet speed on the phone drops very sharply, almost at zero, the screen is duplicated, but the Internet can be said to be cut down. And I also noticed another problem, when I display a video from some site and turn it to full screen, I have black bars on all sides, it does not stretch to full screen.
Who has the same problems? Has anyone already solved them?
Can you check and unsubscribe if Miracast works on this phone with the Internet?