Why is Firefox running very slowly and causing YouTube videos to buffer constantly, even though my internet connection seems fine?

Hello Firefox Team

I'm having a problem with Firefox running very slowly, especially when watching YouTube videos. Videos take a long time to load, keep buffering, and sometimes get stuck while playing. The browser also feels slow overall, not just on YouTube. My internet connection seems to be working normally. I have already tried clearing all browsing history, cookies, and cache, but the issue still persists. I'm not sure if the problem is related to Firefox settings, extensions, hardware acceleration, or possibly a hardware issue with my PC.