Texture is difficult so no worries, I'll try my best to point out a few examples of your mistakes as well as explain how you can go about approaching the exercises. All I ask is that you be a bit patient with me because even explaining it to try and make sense can be a bit tricky, if you still have questions afterwards feel free to ask them.

For examples of you focusing on outlines I'd point to your mushroom, leaf and honey comb dissections.

For negative space your red meat and glass dissections stand out.

In your ceramic dissections and pebbles analysis you focus a bit more on form shadows as well.

I'm glad you made a leaf attempt because it's what I usually use to explain the process and having a direct comparison will hopefully make it a bit easier to understand.

I'd like you to open up this leaf texture and we'll get started. When we ask people to draw a texture they often over simplify the process and just focus on what they observe, while observing a reference is definitely an important aspect they tend to not think about the method we're teaching in this course which is constructional drawing. Now construction does involve observation, so it's not so much that people are doing the entire thing wrong, in reality the methods you chose to draw your textures can be totally valid and even ideal in certain scenarios, they're just not correct in every scenario or what the goal of these exercises have in mind.

Looking at the leaf texture I provided you'll notice it's in black and white, while we shouldn't rely on it all the time converting an image to black and white is definitely helpful, especially in the beginning. People tend to focus in on colour changes and they'll try to recreate them on a page when again we're trying to focus on cast shadows. Red meat is often a good example of this, they'll see red meat with strips of white fat through it and darken all of the red sections of meat and just leave the white fat highlighted, this is an example of focusing on negative space. By converting our image to black and white we deal away with these issues the best we can and are just left with black and white, much like what we're working with tools wise.

Now if we provided this image to someone and said "draw the texture of the leaf you see here" what often ends up happening is people will try and draw every little vein or if they don't have incredible patience they'll try and simplify the image and just capture the main vein and it's large branches, this would be them focusing on outlines.

Instead what we want to do is slow down and think about how this leaf is constructed. If we think about all the veins running through this leaf they're basically just long organic forms or cylinders, while the fleshy bit of the leaf could be described as a flat plane or even a thin box, while hanging off a plant or branch there's probably a bit of a curve involved as well from the weight of the leaf and it being affected by gravity. But even neglecting the fact that it's curved when working super up close like this it's basically just some organic forms intersecting with a plane/box much like the work we did in the form intersections exercise.

Now that we're thinking about how all these forms are positioned in 3D space, we can add a light source much like we did in the organic intersections exercise and depending on the position of this light we can determine where and how intense our cast shadows will be.

Now let's take a look at the leaf texture again (it's here if you closed it) and let's just focus on the main vein as well as the branching vein on the far left of the image. If you look closely along the bottom of the main vein there's cast shadow, and on the branching vein you can see that along the right side of it there's shadow as well. From this we can determine that the strongest light affecting these veins is somewhere to the upper left of the the image. All we need to do now is just simplify which shadows we merge, pick how many of the veins we are actually going to focus on and draw the cast shadows.

An example of what this would look like actually comes up fairly early in lesson 3 but I'll show it to you now so you can have an idea of what the goal is. This is a quick breakdown of how to draw a leaf, the final result on the right implies information by just focusing on the cast shadows, keep in mind that depending on the lighting some shadows will be more intense (they're fairly evenly lit here as opposed to working with a gradient like we try to in lesson 2). While sometimes the end result may not always be easily identifiable based on so few details, it's often just a single part of a puzzle that helps give the viewer information so they can determine what it is. As an example you may not think that looks like a leaf, but if it was green and had a stem and was attached to something brown it would progressively be more and more convincing. By implying information we can save ourselves time/work/stress and prevent the viewer from becoming visually overloaded by trying to capture every single little vein in a leaf that's in the background and not even the focus of our image.

It's definitely by no means an easy task, but if you're able to learn how to focus on these shadows it's incredibly helpful. If you take a look at paintings you'll see lots of information being implied just from brush strokes, shadows, bits of colour etc. Craig Mullins is an example of someone who does a really good job at implying a ton of information.

While the explanation was a bit lengthy, I hope it was helpful. Apologies if you're still left feeling a bit unsure but I do promise it will make more sense with time if you continue along with your studies, sometimes things just take a while to click. That being said if you do have questions feel free to ask and I'll do my best to answer them or bring in Uncomfortable to help point you in the right direction.