Thanks for stopping by the Apple Support Communities. From your post, I understand that when you try to use your camera, the view finder is just black on your display. Additionally, the flash isn't working for the flash light (torch) feature. I'd be happy to help!
Based on what you've described and the information related to your issues outlined in Get help with the camera on your iPhone, iPad, or iPod touch - Apple Support , I would recommend getting the iPhone inspected at an Apple Store or Apple Authorized Service Provider. You can find locations, get contact information, and set reservations here: Apple - Find Locations .
Additionally, you are welcome to reach out to Apple Support directly for more information and to review your options: Contact Apple Support .