If you find that an app is no longer working properly you can easily delete it from the device and then reinstall it again for no extra charge.

After deleting an app, open the App Store, go to the Updates tab and then press the Account button in the top right. From here, tap Purchased and then Not on this iPhone. This will show all the apps you’ve previously downloaded, but don’t currently have on the device.

Tap the cloud icon to download the app again for free.