I downloaded the update last night, and my phone is SUPER slow. When I type, the phone delays and I can only type 3 or 4 letterers at a time. I have to wait about 30 seconds for the text on the screen to catch up to my inputs. The phone overall is slow too. Safari and the other apps take awhile to open up and load, swiping from one screen to another is a pain, the notification bar is hard to pull down too. I updated my dad's phone (also an iPhone 4) to iOS 7, and his does not have any of theses problems.
Is there a way to fix this?