Why isn't my keyboard working

You best best is to replace the keyboard, but most likely no one sells parts for this. You can just buy another same model and bring it to a repair shop to have them swap out the keyboard for you. Expect to pay about $40-80 for it.

Is this working ? Yes or no.

Check and see if there is any dust or lint or other rubbish in between your keys. Clean it with canned air or with isopropyl. Try wiping your cache partition and restarting as well.