Dell Vostro 14-3468 Keyboard stopped working after few days

I have a Dell Vostro 14-3468 laptop with a 7th Gen Core i7, Windows 10 and 8GB RAM. I have already replaced the keyboard three times, but after some time, certain keys just stop working again. On top of that, the laptop’s fan keeps running continuously. What could be the real reason behind this? I’ve had this laptop serviced multiple times, but the problem keeps coming back. There has to be some underlying issue causing this again and again.

Also, what exactly are “memory” and “page file”? What’s the difference between them? I’m mainly using this laptop for gaming, so I want to understand how all this actually affects performance.