Hey Himanshu!
My name is Ravi, an independent advisor and expert user. I am happy to help you. :)
I understand how annoying it can be when the keyboard keys stop working randomly.
Try the keyboard troubleshooter.
1). Open Start and select Settings > System > Troubleshoot.
2). Select Other Troubleshooters.
3). On "Keyboard", click "Run.
If it doesn't help, try these steps to uninstall and reinstall the keyboard driver:
1). Right-click Start.
2). Open the Device Manager
3). Expand the Keyboard from the list.
4). Right-click on the keyboard
5). Select Uninstall
6). Restart your computer
Feel free to get in touch again if you have any additional questions.
Cheers,
Ravi