The machine is laggy and the SMC reset is not working Recently my 2015 MacBook Pro started to lag a lot, especially the graphics. The animations are really slow and breaking up sometimes. Someone suggested an NVRAM reset followed by an SMC reset will fix it.   

The NVRAM is working. But the SMC reset is not. I tried to hold  Ctrl ⌃    Opt ⌥   Shift ⇧   + the power button up to 30 seconds. Still, it's not resetting (The color of the mag safe connector is not changing.). Any idea what's happening?

A screenshot of the activity monitor:
Have you tried to boot into single-user mode ( boot while holding down the command and the S buttons untill you see a black screen ) and then run " fsck -fy " command? 

This will run some diagnostics and make any changes needed. When it is finished it will say  drive appears to be ok OR changes were made. 

You then type " reboot " ( without quotation marks ) and it will reboot.

Troubleshoot Your Mac With These Hidden Startup Options

Use safe mode to isolate issues with your Mac