how can i open the camera

Hello ~ Try this:

Force restart iPhone - Apple Support

Also close the camera app …may help with flashlight:

Close an app on your iPhone or iPod touch - Apple Support

If neither help:

Genius Bar Reservation and Apple Support Options

~Katana-San~

If the flash isn't working

On an iPhone 8 or earlier, swipe up from the bottom edge of any screen. Tap the Torch button . If the LED flash doesn't work as a torch, contact Apple Support for help with your iPhone, iPad or iPod touch.

If the camera or flash on your iPhone, iPad or iPod touch aren't ...