The strong yellow, blues, and reds are very contrasty and resonate... at the expense of losing interest in your subject which isn't a good trade-off. With portraits, what the person is wearing and the background you put them against is critical. You want outfits and backgrounds that don't contrast and don't draw attention.
In the car pic, look at alllllllll that stuff in the background. None if it has anything to do with your subject. Leave it out. Also, the front of the car has lost most detail because it is underexposed (you exposed for the background). You generally want your subject to have detail.
These are two very important concepts to harness so you did well choosing these two photographs to post for feedback.