Hi Karlo,
Looks like you are getting some good directions from other members. I would agree with most of the comments. The details will make a big difference. Your camera angle is really close but if you look at the left side where your building ends and the photo building starts you can see the two vertical lines separate from each other. It is minor but throws things off. If you are using a vray camera adjust your vertical shift to compensate. One item to keep in mind is that an object can not cast a shadow within a shadow, unless the item on top is transparent to some degree. So your car coming out of the build on the right side would not cast a shadow. Spend a little more time blending the edges of the image and keep up the good work.