Your organic forms are looking great! Big fan of the piles. There are two things I think you could improve upon: In the image with the shaded boxes some of the converging lines are converging in the wrong direction or slightly wobbly. I know the exercise is to do this freehand, but I think you should use a ruler to extend the lines you already have to make see where your vanishing points are so that you can find mistakes yourself without needing people to give you critiques and thereby give yourself a feedback loop. In the images with textures, I would use light and shadow to communicate textures. If you start by mapping out the shadow and light shapes and then apply the diagram you uploaded as a transition from darks to lights. If you insist on sticking with line to describe form, I would curve the lines to match the forms (you did this well on watermelon and cactus but the wood and bark are a bit too straight and feel flat). If lines are evenly spaced around a round object the lines in a drawing get closer to eachother the further you get from the viewer. Hope this helps and if anything doesn't make sense or you have other questions, just reply and I'll try to get back to you :))

Great exercises!