mx330 is certainly not meant for great gaming 

So let nVIDIA decide whats the best settings for your GPU. 

Install GeForce Experience and Download recommended drivers 

In Geforce choose to optimize the game and It will set game settings (for supported games) best tested for your GPU 

PS : Please open support assist > troubleshooting > I want to troubleshoot my PC > Check a specific piece of hardware. Run a stress test on GPU. 

I did a stress test. And likewise, gpu usage was 100 and fps decreased. I get 15 or 20 fps from the game I previously received 60 fps. And I've been doing it in every game for four days. 

Than only other thing I can consider 

1 BAD or Corrupted OS 

2.Bad GPU ( soldered on Motherboard) 

3.Temperatures 

Start with checking temperatures while running stress test on both GPU and CPU 

If temps are below 70-80 degrees than Reinstall OS

If temps are highers it's time to open the Machine and reapply thermal paste beneath the heatsink.

I also Exactly have the same problem I have the same laptop with i7 processor whenever i play a game fps drops to single digit and makes the game worst and laggy