sounds like a guessing game, maybe "post a video and check the task manager"
but mozzila is no good for gaming?, could try in safe mode~
try IE11, maxthon, opera..

disabling hardware acceleration might help,
could try browsers with their own flash,
and there r different version of flash around~

get new IP?
cmd >
ipconfig /flushdns
ipconfig /release
ipconfig /renew

cleaning temp files might remove some evil junk
disabe windows update, firewall,
and check ur task scheduler !
It's ur country fault! >.<