Camera Issues
my camera does not work when I use the portrait mode, the light dims and phone hangs. Then using the photo mode while zooming in it hangs its so annoying.
iPhone 7 Plus, 13
This sounds like a potential issue with the telephoto camera on your iPhone 7 Plus.
There are some steps over at If the camera or flash on your iPhone, iPad or iPod touch isn't working – Apple Support which may be of some help to you.
If these steps don't work for you, I'd recommend you Contact Apple Support to book the device in to your nearest Genius Bar, Apple Authorised Service Provider or send in for repair.
Best of luck!