As a whole, you're definitely off to a good start. There are a number of areas I'll get into where your work can be improved, and we will certainly work on that further, but this is indeed an extremely difficult lesson, as you've observed yourself.

To start, you're doing a great job with the organic intersections. You've established how they interact with one another in 3D space in a believable manner. I have just one recommendation - on the top pile of the second page, you appear to have added two smaller sausages at the base (or beneath) an existing one. When doing this exercise, always place new sausages on top - never underneath. Reason being, we always want our upper forms to rest on top of the existing forms so their silhouette can be shaped such that they're actually slumping over top. If said form has already been drawn, then its silhouette cannot be modified to reflect the presence of forms beneath - so you're basically just asking to draw forms that will not feel naturally present, and will stand out from the others.

Moving forward, your animal constructions definitely demonstrate a solidly developing understanding of how the core elements of these constructions all fit together, and how they relate to one another in 3D space. I can also see a number of areas in which your drawings improve as you move through the set.

One such area is in head construction. At the beginning you definitely approach head construction correctly, in that you're fitting all the pieces - the eye socket, muzzle, etc. together like pieces of a 3D puzle, but the way in which you draw those eye sockets tends to be clumsy, not quite being shaped correctly and often featuring unsteady curves rather than clean, straight cuts. I suspect part of this could be simply that you're drawing too small on the page - this is a common cause for clumsier linework, as it limits our brain's capacity to think through spatial problems, and also limits how easily we can engage our whole arm while drawing.

Later, as you get into the horses and deer, the structural integrity of the heads definitely improves. It's still not perfect - and again, don't be afraid to draw bigger, even if it results in just having one drawing on a given page - but it's definitely moving solidly in the right direction. Keep working on dropping in a ball for the eye, and building up eyelids around it. In case you haven't seen it yet (based on your work, you may well have), be sure to check out this overview of how to approach head construction.

Moving forward, one point I noticed quite a bit was that in a lot of areas, you rely very heavily on contour lines - specifically the kind that sit along the surface of a single form (as opposed to the ones that define intersections between forms), in a manner that suggests that you're adding them out of reflex, rather than with a specific goal or task for them to accomplish.

The thing about contour lines of this nature is that they suffer from diminishing returns - with each subsequent one being vastly less impactful than the previous one - and also that they can only make a form feel three dimensional on its own, and cannot help make them feel 3D in relation to other forms. Conversely, the intersectional contour lines do a great job of creating these kinds of 3D relationships between forms, as can the actual silhouette of a given form. This comes up a lot when we look at the additional masses, which are an area you struggled with a fair bit.

The thing about the additional masses is that the way they're shaped - their actual silhouettes - is what matters most. You've frequently piled contour lines onto these, but unfortunately what matters most is how they're shaped when initially drawn, and how that reflects their relationship with the existing structure to which they're attaching. In order to do that correctly, we need to first think about how those additional masses exist on their own. By default, they're really just simple balls of meat, existing in their simplest state, consisting only of outward curves, until they actually press against another structure. When they do so, they take on inward curves, and their silhouette becomes more complex in the areas of contact, as shown in this diagram.

The idea here is that we need to be keenly aware of the specific nature of the structure our masses are pushing up against. It's not enough to just draw an arbitrarily complex line for that part of the silhouette - the line has to reflect precisely the forms it's interacting with, to convincingly give the impression that it's actually hugging and wrapping around it. Furthermore, every bit of complexity (remember, inward curves are complex, outward curves are simple) has to be due to the influence of some other form making contact. If, like along the outer edge of such a form, it's not touching anything, then it has to curve outwards.

Here are some examples, on your bears, where those additional masses could be handled much better. Note how I don't need any additional contour lines - the shape of the silhouette is enough to carry the illusion that they're 3D. Here are some further examples looking at the deer - specifically with their legs. Don't forget the demonstration I showed you in my lesson 4 critique, of this dog's leg. Note how all those additional masses wrap around the structure and come together to create a bunch of integrated 'muscle'-like forms.

To that point, I definitely noticed that you're pretty inconsistent in applying all the steps of the sausage method consistently. Most specifically, you tend to forget to define the joint between sausages with a contour line.

With that, I'm going to assign a few pages of revisions below so you can apply what I've explained here. You are on the right track, but I expect you'll be able to do even better. Remember to draw big, so you can give your arm and brain plenty of room to work.