Seeing your previous works and this one, i notice that you dont follow the original proportions of the parts (the front wheel in this case) or the whole car you're using. To avoid that next time, when free transforming something, hold the Shift button while resizing etc.
Also i see edgy selections on this one - rear wheel for example, which also isnt positioned well. To avoid edgy selections use the pen tool on feather radius 0.3-0.4.
And last, dont make the chop bigger resolution than the original one, so you wont loose the quality of the image or having to brush/rebrush.
Although the mistakes i pointed, you fitted and blended the car well to the new bg and atmosphere, but try using little less lens flare so it doesnt look fake.
Keep practising and try to make little changes step by step at first, until you make them perfect, and then go on with something bigger, and so on. Practise is the key and you are getting better. Good luck on your next one !
