Why is my camera taking black pictures?

A couple options here...

If these are photos you took before (and know that they came out alright) then there is probably a software error causing all your photos to appear black. You can try transferring the photos to your computer and then resetting the phone to factory conditions. NOTE: this will wipe all the files on your phone so make sure you do a backup through android before you hit reset.

If you mean that the camera has only been able to take black photo's (so there are no original photos - just blank files), it is most probably a hardware issue such as the camera's shutter being stuck. When this is the case, it's actually very easy to replace the camera! Follow the replacement guide found on the main device page here: Huawei P6-U06

Troubleshoot your camera problem here: Huawei Ascend P6-U06 Troubleshooting