I have ap that stops when I chk its messages

Could you be more specific? What app? Does it crash? Freeze? When was the app last updated?

Try deleting the app ( hold your finger on the app icon until it jiggles then tap the x on the top left corner of the app) & then redownload it to see if that corrects the problem.

Here's what I try when an app doesn't work properly.

1. Quit the app. Double click the Home button to show the screen with running and recently used apps. Each app icon will have a sample page above it. Flick up on the page (not the app icon) and the page will fly away and the app icon will disappear. This quits that app. Then start it again.

2. If the first thing didn't work I would quite the app again but then reset the device. After quitting the app press and hold both the Home button and the Sleep/Wake button continuously until the Apple logo appears. Then release the button and let the device restart. You will not lose data doing this. It's like a computer reboot.

3. If the app still doesn't work try deleting the app and reinstalling it.

4. Still doesn't work? Contact the developer.