Run Keyboard Troubleshooter:
Settings app > Troubleshoot tab > click on the Additional troubleshooters tab > Locate the Keyboard troubleshooter > Run
Make sure Filter key is off.
Settings > Accessibility > Keyboard > Filter Keys > Off
Try an external keyboard to test the issue. If all the keys are working on external keyboard then it may be a hardware problem of laptop keyboard. In that case visit the authorized service point.