my internet is working fine but none of my apps are working

Reboot and then try your apps again.

Reboot the iPad by holding down on the sleep and home buttons at the same time for about 10-15 seconds until the Apple Logo appears - ignore the red slider if it appears on the screen - let go of the buttons. Let the iPad start up.

Check in settings to make sure your date is right. Do this by going to settings> general> date and time and press set automatically

if appleID in settings->itunes & app stores is changed from the appleID the apps was downloaded with non of them will start