Q: Why my iphone5s after updated to ios 8.4.1, my iphone will hang and have many lines in the screen?

Hello, Ckhou.  

Thank you for visiting Apple Support Communities.  

I understand that your iPhone display is not functioning as expected.  Here are the troubleshooting steps that I would recommend going through for this issue.  

Screen

Get help with the screen on your device if it has any of these issues:

• The screen is too dim, too bright, or you see only faint images
• You see a solid color screen (black, white or blue)
• You see lines, missing sections, discoloration, or poor image quality

Issue not solved

If you still have an issue with your device, contact Apple Support.

Get help with hardware features on your iPhone, iPad, and iPod touch

Cheers