We pay for a wifi speed of 100mbps although it has never been close to that (~10-25mbps).
But suddenly one week ago the wifi dropped to speeds between 0.5 and 3mbps, and this number is only marginally higher when using a wired connection. We can no longer stream videos properly, nor access online education. We did not have any issues prior to one week ago.
How can we fix this and get a speed a bit closer to what we actually pay for?
No, you don't pay for WiFi speed. You pay for broadband speed to the Hub, and that should be what you get with a wired connection. WiFi speed is not guaranteed and depends on a number of local factors. It can usually be improved though.
What speed do you actually get with a wired connection?