Now that i've considered what the problem is and some possible ways to solve it, I can see the issues much more clearly. It probably won't take a full image study to get the answers, after all. I can focus on just the places where the space is confusing.
See the short triangle of light (point upward) in the center of the scene? The job is to get it to separate from the similarly colored light rectangle it's adjacent to (dead center). I don't want to make one much darker than the other or I'll violate the consistency of light and shadow, but a little color difference along a hard edge would certainly do the trick. There. Problem solved. No study necessary. Sometimes just clarifying the question provides the answer!
Even when you are sure you're ready to launch into a proper painting of your subject, it's still a good idea take a good, long look at the relative values first. For example, just how light is that "white" car? Is it darker than the window?I like to bracket each shape by filling in the sentence, "This is lighter than ____, but darker than ____."
Pick one of these images, or use one of your own. Try to identify what looks tricky to you, and clarify what makes it tricky. Plan a study that will give you the information you need to proceed to paint the scene with confidence. Take notes! Have fun.