First, your organic arrows don't give the feeling of depth that's needed. Watching closely, we can see that you tried, but that's not convincing at the first look. Try to make more regulars and flowing ribbon, like int the examples on the exercise page. Also, the shadows must be in the inside of the fold, not outside: it's the shadow of the part of the arrow who's behind.

Your organic shapes can be improved a lot: the ellipses aren't centered on the minor axes, they often never touches the edge of the form, and they're sometimes wobbling. Contour lines is what will give the feeling of 3D, so they're even more important than the shape itself.

The texture analysis part is half understood: the left square is good, even thought you could focus a bit more on the shadows. However, you've done the black to white gradient in the right rectangle too fast. The transition between full black and texture black is way too strong, and the 3 rectangles didn't look like the original texture you've drawn. Take more time to do it, and keep watching the reference. Also, try to fill the space more, the rectangles are too empty, especially on the dark part.

Same thing for texture dissection. First, focus on cast shadows and little bumps, not lines. Second, try to wrap your texture around the form, it's not a flat surface. Third, be more patient, take your time. You looks kinda hurry when you've drawn this: it's hard and it takes time, so don't rush it.

Forms intersection: I'm sorry, but your boxes are really bad. Once again, take your time, think about vanishing points etc for each box. A box isn't some random lines connected to each others, its the representation of something who exists and has right angles, think about it when you draw a box. Then, when you'll understood and applied that, think about the intersections of the forms between each others, but that's the next step.

Your organic intersection are pretty hesitating too. Your lines are woobling, you didn't drawn the shadows. The second one is way better, but put more shadows, not only at the end of each form.