Q: i cannt activate  my iphone5 after ios update 9.3 please help me

Seems like Apple has temporary  troubles with their activation servers. Lots of users report similar issue on older devices.

Recent info  : If you can't activate your iPhone, iPad, or iPod touch after installing iOS 9.3 - Apple Support

http://www.imore.com/apple-working-ios-93-fix-older-iphone-ipad?utm_medium=slide r&utm_campaign=navigation&utm_source=im

http://9to5mac.com/2016/03/24/apple-releases-new-build-of-ios-9-3-for-users-of-o lder-ios-devices-affected-by-bricking-bug/

Hoppefully Apple will shed the light on it soon

Same problome here

Apple has issued a fix for this problem. Connect your device to a computer running iTunes 12.3 or later and connect the device. An updated version of iOS 9.3 will be installed that corrects the problem of not being able to activate the device. You will still need your Apple ID and password however.