First, try [[Troubleshoot Firefox issues using Safe Mode|running Firefox in Safe Mode]]. According to your system details you are running an adblocking extension, which can cause video playback issues. The same could be said for a VPN (which you appear to be using), since that could significantly slow your internet speed. You should also [[Upgrade your graphics drivers to use hardware acceleration and WebGL]]. if that doesn't help, [[Upgrade your graphics drivers to use hardware acceleration and WebGL#w_turning-off-hardware-acceleration|try disabling hardware acceleration]] to see if performance improves. I'd recommend taking a look at the [[Fix common audio and video issues]] document to see if anything there solves the issue for you. If nothing there helps, try [[Fix video and audio playback problems on Firefox for Windows|installing the Media Feature Pack for Windows]] that Firefox requires in order to play video content. Hope this helps.