It's a good start since you focused on just one thing for start, and that is bg change. But here's the thing, you did the selections ok, but you squashed the car and it isn't in perspective with new bg.
I've drawn you perspective helper lines, green ones are from bg, and yellow ones are from car, you can easily see they don't match..
If you are not sure if the car fits you can draw those lines by yourself by connecting things that are same level, you know that from real life, like the vents on the front bumper, they are always simmetrical, the wheel centers are also a safe bet for the side helper line.. for the bg, you can use lines from sidewalks, buildings, etc...