With the upgrade of iOS7 (the latest major version of iOS) on iPhone 4 many users have complained that their iPhone is not lagging in UI and the applications are also crashing. In short they are putting it as their phone has gone really slow. One of the user complained on the Apple discussion that when he wants to call anyone then he has to wait for the iPhone to respond for about 10 to 12 seconds on every step. Now this is something very serious because the lag at this rate makes your iPhone completely useless. So, there are the steps which can help you to deal with this problem.
How To Fix It
Upgrade your iPhone 4 to iOS7.0.3. This is the latest update of the iOS7. This update will fix many of the fixes on your iPhone and the lock-screen bypass problem which created a lots of problem among the users. This update will reduce the lag to a huge extent.
Try to close the applications regularly when you exit an application, make sure that when you double tap the home button you don’t a huge list of application in the row. Following the same logic in mind, delete all those application which you seldom use.
If the lag is unbearable, then take the backup of your iPhone 4 and then restore it with the backup.
These steps will really help you keep your iPhone4 stable and reduce the lag to a huge extent. After restoring the device, it responds really well but then after a month or two it might start doing the same things again. So, you can think of repeating the above again and again after an interval of 2 or 3 months. Please let us know if you face any problem while dealing with this issue.