hi,,,, whats the make and model of the pc so we can look at the spec ,,,
gaming and watching vids are resource intensive and lack of resources could be the cause of the slowdowns and screen freezes.
Both things your doing run better with a stand alone graphics card installed,,, if your pc does not have one it will be using the systems RAM and onboard graphics which will struggle with high end games and video.
it is also common to have a good few svchost.exe processes running,,,,,,, BUT, it could also be sign of a virus.
a clue to what a particular svchost.exe service is ,,, open task manager,,, right click the svchost.exe using the most cpu and select go to service(s) and post back what service it is from, this could help narrow it down.
you can shut down non essential services,,,, visit a site called the black viper,,,, select your OS and take a look.
I would start with your start up programs first though,, these are programs that run on the start up of the PC,,,
most are not need to run on start up at all,,,as an example on one of my pc's i only have 2 things on start up,,, the security software,,, Avast home free and MBAM Full version (Malwarebytes)
how to check and stop them,,,
if your not sure about what they are then google its name,,, if you want one back on start up reverse the actions to stop it.
And last but not least,, just as a precaution run a scan with Malwarebytes free version to check for nasties,,,
down load the free version,,, update its virus definitions then run a full scan
dont forget to get back to us with the make and model of the pc,,, or its spec's