It would be better if you used something from a professional photography like THIS and not amateur photos taken from google. quality is usually bad and the angle is shit. It will take some time to remove the old car from the background but it's worth it
When you find background with car and similar angle, as your base, then you put your car over background car. Then we will help you to use clone stamp tool, brushing, copy pasting. Now do it. go and find normal background, then we will help you