Camera failed

Just try these. Press and hold your camera app icon. Click Storage > Clear Cache and Clear data.
(This will not erase any of your personal data, but change your camera settings to default).
After that, wipe your cache partition.
(Switch off your phone. Press and hold, power button, Bixby button (if you have that) and volume-up button for 4-5 seconds till the phone turn on and boot into the recovery mode.
Use volume keys to navigate to 'wipe cache partition.' Use power key to select and confirm. Then reboot your device. Normally, this will not effect any personal data or settings.)