Can we replace graphics card in sony vaio

I'm afraid you're out of luck. It's usually impossible to change a graphics card in laptop, and it's no difference in your case. Only a few gaming laptops got such a feature, and they cost around $2000-$3000.

However, if you want to play games, there might be the only solution: build a desktop. I know this sounds pricy, but for as little as £400 you could build yourself a decent gaming machine.

no, you can't.