Hello and sorry you're having problems. You can try a hard reboot of the Kindle to see if that helps- but beyond that it would require repairs (about $130 to have the screen replaced), and is usually better off to purchase a new one.
The problem you're having is often due to the software in the Kindle locking up and it needing to be rebooted. To do this, simply press and hold the power button on the Kindle for 30 full seconds, then release and wait a full minute for it to reboot. Do not press anything else during that minute. If this does not cure the issue, oftentimes the reset procedure needs to be repeated several times for it to force a reboot.
If that does not work then it would be more cost effective to replace the Kindle, and you can still download all of your books onto the new device without having to purchase them again.
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