First off your photo epitomises the usual mistakes made by rookie photographers.
1) Unaware how the camera's meter works - the subject are mostly in dark tones, fooling the camera's meter into thinking that more exposure is needed than necessary
2) Not knowing the camera enough 1 - one way to counteract such problems is to quickly bracket exposures. We don't know what exposure mode was used but you can reassign one of the e-dials to change exposure compensation on the fly with a flick of the finger
3) Not knowing the camera enough 2 - confirm exposure with the histogram, use the bright/dark area to show where detail is lost or not available, keep D-range on to expand the dynamic range and reduce the occurrence of overexposure.
4) Shooting in jpeg rather than RAW - loss of quality upfront and not capitalizing on the camera sensor's full capacity, limits on recovery during post processing. As there is already loss of detail and color information, it is a lot harder to get acceptable results without color artifacts, clipping, loss of detail, loss of contrast and limitations on image size.
5) Not knowing enough by way of post processing - with the right tools and a clear idea on what it takes to salvage a photo, one can try to correct the obvious problems with the photo.
My quick and dirty 30 second fix.