Hi, jacklyn152. We understand that your keyboard is showing larger than the screen and you're unable to rotate the screen of your device to resolve this. We'll be happy to assist you.
To start, one instance that may cause part of your screen or keyboard to seem larger than it should be would be the "Zoom" accessibility feature. Many applications, such as the App Store may not support rotation if you're using it on an iPhone.
You can check your Zoom settings on the device by following the steps in this article: Zoom in on the iPhone screen
Thanks for reaching out to us!