Looking over your work here, I think there is indeed a lot of things you could have done better. I'll go through the exercises one by one and address the issues as I come across them.

Starting with your arrows, they're flowing with a fair bit of confidence and fluidity, although it appears to me as though you've tried to draw the arrow head all as one continuous stroke for some reason. So while the ribbon is largely fine (although keep in mind that as the ribbon moves away from the viewer, the spacing between the zigzagging sections will get narrower), the arrow heads tend to look like a mess, and for no good reason. The second page is somewhat better in this regard, but applying the ghosting method (as you should for each and every mark you draw), and generally taking more time would help a great deal.

Your organic forms with contour lines are a bit split up. In your first page - the organic forms with contour ellipses - the sausage forms are generally decently done. There are some issues specifically in getting your start and end point to flow into one another properly when drawing around the whole sausage, but you're striving quite well to keep the sausage forms "simple", as described in the instructions. There are some that definitely end up falling off that wagon, with one end smaller than the other, but most are coming along fairly well. Looking then at the organic forms with contour curves, it seems that the success rate with your sausages drops somewhat, with more of them ending up with one end somewhat misshapen. Again - take more time in executing these, as you're clearly capable of doing them well, you just aren't necessarily putting in as much into each individual one as you could.

Looking at the contour ellipses, there is a tendency for them to come ou a little bit stiff and uneven at times, so again - make sure you're applying the ghosting method here to ensure that you execute them with confidence, without hesitation or fear of making a mistake. Mistakes happen, but if you hesitate in anticipation of one, you'll stiffen up.

As a whole the contour lines appear to be pretty smooth and confident, though you're generally drawing each one with the same degree over the course of each sausage's length. The degree of a contour line basically represents the orientation of that cross-section in space, relative to the viewer, and as we slide along the sausage form, the cross section is either going to open up (allowing us to see more of it) or turn away from the viewer (allowing us to see less), as shown here.

Continuing onto the texture analyses, the good is that you're clearly focusing primarily on the use of clear black shapes, rather than outlining your textural forms, but I suspect that you're not necessarily designing those shapes based on the actual shadows cast by the textural forms present on the surfaces you're studying. That was a bit of a long sentence, so I'll try and clarify: the black shapes we draw are, each of them, cast shadows, the result of some forms present on the surface of an object blocking the light, resulting in a shadow being cast upon the neighbouring surface. We're capturing those shadow shapes specifically to imply the presence of the form itself, without actually drawing it.

Looking at the pineapple especially, I'm not really getting the impression that you're thinking about the textural forms present along the surface, and how to actually imply their presence. It seems to me you might be skipping a few steps, and just trying to draw arbitrary shapes that may relate to aspects of the texture - but not necessarily as being shadow shapes.

Overall, I think you're falling short when it comes to actually observing your reference. Looking at your results, in the study areas you appear to be working a lot more from memory - maybe studying your texture all at once, then spending a nice long time drawing the result. As explained here, the moment you look away from your reference, your brain has started throwing away all kinds of important information, leaving you with a much more simplified idea of how things looked. Then you go on to replicate that on the page.

Instead, we need to look back at our reference constantly, only putting a single mark down at a time before returning to the reference to figure out what we need to put down next. This applies to the gradient as well, on the right side of each row. Your gradients include highly simplified shapes, but they appear more haphazard and random rather than actually reflecting the textures you're attempting to study.

The main takeaway here is that you need to spend a lot more time observing and studying your reference, and do so continuously even as you draw.

Moving forward, it appears that you haven't included the dissections exercise, two pages of which were assigned in this lesson.

Moving onto your form intersections, what stands out most of all is that your linework is pretty sloppy - you're not really applying the principles of the ghosting method, you're going back over lines repeatedly (which is a bad habit - if you make a mistake, leave it alone), and you're leaving gaps all over which undermines the solidity of the forms you're drawing. As a whole, you're not really adhering to the principles covered in the first lesson when it comes to mark making. The ghosting method is a critical part of this whole course, and it should be applied to every single mark you draw, without exceptions. It requires you to first think about the line you wish to draw, to weigh what its purpose is and how to best approach drawing it. Then it requires you to put time and effort into getting comfortable with the motion required to draw it. And finally, it requires you to execute it with confidence, free from all hesitation. If you make a mistake, no big deal - mistakes happen, but you'd put in the time required to reduce the changes of that happening. What you've drawn here has included very little, if any, of that. It appears more haphazard, and rushed. I see a few dots here and there where you may have gone through the motions of the ghosting technique, but I don't think you quite grasp what it's about.

I recommend you read through this explanation I gave to another student about precisely how it works, and why it's so important. Looking at your box challenge you are 100% capable of executing your lines with far more confidence and care than you've demonstrated here.

For the intersections themselves, in the last page you're getting a decent start on it. In the other pages, you may not have fully grasped how those intersections work (you were just drawing back over the existing lines), but you seem to have made some progress in the end there. The key is that the intersection lines sit on the surface of the forms themselves - they don't coincide with existing edges, but rather produce new ones. For example, if we look at the sphere intersecting with the box in the bottom right of this page, that's actually entirely correct - you've followed the new path that is shared by both the sphere and the box. But if you look at the same box intersecting with the cylinder, all you're doing is going back over the existing edge.

In the future, don't draw the intersection lines with a different coloured pen. This makes the intersections seem like they're some separate analysis - it's not. The intersection lines themselves are a part of the drawing, they're part of these forms as they exist together in space. It's like if you have diferent metal primitive forms, and you're welding them together - the intersections themselves are the welding marks.

Lastly, you appear to have put very little effort into actually drawing the contour curves on your organic intersections, so I'm just going to leave that one alone. I will happily critique work that is done to the best of your ability, but this is very clearly not.

Now, as a whole you're showing areas of both weakness and strength, but more than anything, you're showing a lack of patience and care in executing your marks to the best of your ability. So, while we could get away with me just assigning specific exercises for you to redo to focus on the particular issues I highlighted above (plus the missing dissections), I think it would be better in the long run to have you redo the whole lesson, and to submit it anew, rather than as revisions.

Very little of this has to do with you being "dense" as you put it yourself. You have already demonstrated yourself to be able to take the time to execute your marks with planning, care and confidence. You very clearly have it in you to invest the time that is required for these tasks. You have made the choice not to give each exercise that time, however. It is better you understand that now, than to have you doing this for all later lessons, requiring these lengthy, laborious critiques once again.