Yeah nothing much has happened here, you pre-tuned a car in 3D Tuning app, you changed the color badly, the bodykit quality is worse than before, the wheels bad and blury, the shadow under the car is very messy and unreal! There are a lot of jagged edges and the reflections barely have anything to do with the background
Sorry but this is a very bad attempt at chopping! Before posting again, try posting the picture into the "Work In Progress" forum and get some advice from others to get some help!!