How do I fix my touchscreen?

If your iPad does not respond to touch in some areas of the screen - and does in others - you likely have a screen hardware fault that requires investigation/repair.

If cleaning the screen does not resolve the issue, you would be best advised to visit the Genius Bar at your local Apple Store or Apple Authorised Service Provider (AASP) - where the technicians will be able to test and assess your iPad - and you can explore your available options for remedy:

Genius Bar Reservation and Apple Support Options - Apple

if it was me then I would

try restarting the ios device Force restart iPhone - Apple Support and check if it resolved it if it did not

then I would try Restore your iPhone, iPad, or iPod to factory settings - Apple Support - Apple Support if that did not resolve it then I would

contact apple about repair Contact - Official Apple Support