keys from 1 to 9 and their upper cases not working

But my keyboard is working fine. Just these keys are not working. Why do you think they stopped working?

Thank you so much, unfortunately I do not have an external keyboard and cannot possibly replace anything according to the article you provided. I do not see well and I do not understand what should be done. My machine is almost new and I am afraid to damage it. I have a couple of more details, if they help to diagnose the problem: yesterday the keys started to work again, just out of the blue. In a few hours, they stopped working again, but it was possible to type the number if I hit the key hard enough. Then they stopped working completely. Now I have my keyboard backlight set to switch off after sec of inactivity. With the backlight off (as keyboard inactive) if I hit any of the numbers, the backlight does not turn back on, although it does if I hit any letter key. That means the keyboard does not recognize the number keys. So what should I do? Bring it to the repairs and tell them they should replace my upper case?