FPS issue in GAMes

[SYnviv06]

dell inspiron 3543 with i5, 4gb ram and 2gb Nvidia 820 series. suddenly games lagging

 

[AtomSphere]

Please tell us in details if there is any recent changes with your softwares.
Did you update your display, audio, bios drivers? Is there new windows update available?
Which windows are you using?
What is the game in question?
Recommend to start with observing your CPU idle clockspeed.
Malwarebytes scan your computer and avast to remove any harmful programs.

I just solved my fps issue recently and it boiled down to malfunction of software managing my CPU clockspeed.