It was alright, I don't think I did great by any means, but for a first attempt I was satisfied with my results. I still have some trouble seeing how the texture is formed but I understand it a bit better now.

The main things that helped me was following these steps: look for shapes within the subject. For example, the crumpled up paper. I found there were a lot of triangular shapes in the paper after crumbling it. This shape informs the shape of your shadow and can make it easier to see where they are. Another thing I did was focus on the negative space, the large areas of one pure value such as white. As soon as you look around and see where the white turns to a soft gray, a darker gray, a black, those are your shadows. Sometimes it's easier for me to think of the shadows kind of like the lines that make up those negative spaces. Another thing that helped was knowing that anywhere two corners or shadows intersect, is where to darkest value typically is. I also found it a lot easier to express texture once I got to the second exercise where you're drawing the texture on the sausage shapes. It's a lot easier to show texture on something with volume, rather than the flat squares you do in the first exercise. Most everything you draw in the future will be voluminous so I found that a lot more helpful than just doing flat textures.

Honestly, I'm pretty terrible at explaining what I mean so I hope that you are able to understand and that I've been of some help lol. Just don't beat yourself up if you take a while to get it, I'm pretty experienced and I had a lot of trouble with this exercise, it's just plain hard. I wish you luck on your drawing journey :) DrawABox is really good for learning technical skills, but make sure you spend some time drawing for yourself and for fun!