Regarding gpu.

Blazeray

I m having acer nitro 5 rayzen .8 gb ram and 4 gb dedicated graphic .
While playing any game i am facing lags and a low fps.Even after switching the graphics and updatind the drivers the problem is not solved. The game are running smoothly on my other lapton with only 2 gb dedicated graphics.

tobimaru

This can be a sign of high temperature and thermal throttling. There's a free program linked in my signature 'GPU-Z' that lets you monitor the CPU and GPU temps while gaming to verify this. If that's the case, there are several things you can do to improve the cooling of the Nitro 5.