All the games started lagging suddenly [closed]

Suddenly all the games started lagging , I have tried everything, read everything and its been more than a month now. Installed new windows and even set my system setup to factory settings and installed the game only (nothing other than drivers), emptied my hard drive but nothing worked.

1. Whenever I played a heavy game my system fan would start moving faster and it won't lag and a lot of heat would come out of my pc but now it doesn't heat up whenever I play a heavy game it just lags from start and system never heats up a little and fan moves with regular speed.

2. This has also affected my pc speed so it just runs slower. Even though the startup processes aren't that much.

PC specs:

Dedicated Video Memory bothers me. Please help me, I am not very good at these things, I am learning about PC. Even games like Astroneer which shouldn't lag on my PC lag every second. Its like constant lag.