Try to isolate the middle value shapes from the darks and lights.
It may be easier to make value comparisons without the colors to distract you. Squinting also helps see value more than hue.
The roof shingles are lighter than the weeds in shadow, but darker than the sunlit weeds.
Try making a monochrome study of this painting or one of the photos that follow. There's a twist to this exercise, however; Start by identifying the lights . If a shape is closer to white than it is to middle value, leave it white. Paint everything else middle value.
Then, paint the darks. If a shape is closer to middle than it is to black, leave it middle value.
Read this again, and take your time.