Bandwidth

I get tired of watching the spinning circle pop up 4-7 times during a 45 min TV series episode.  I pay for the "up to" 900 mbs speed but seems to still happened.  It happens mostly with the Xfinity Flex box though the Roku and Firestick.  For my trouble shooting it is the wireless bandwidth that is having issues.  My VoIP phone will still work when I have wireless drop at my desk (I do Teams or Zoom calls and will drop all together or have to close video due to poor internet quality message which is very frustrating).  I have contacted support several times, it is pretty much same response - rebook your router (V7 version) and then they want to update the signal, seems to help for a couple of days then back to spinning circle or complete lock up the video stream.

So Xfinity what is the solution or how much bandwidth do I need to have a reliable video stream?