It may have been a struggle, but what you've shared here largely shows a pretty strong overall understanding of the core principles of the lesson, and how construction should be approached. There are a few things that I'll point out, but all in all your work here is very well done.

Starting with your organic intersections, these largely do a good job of establishing how each form interacts with the forms around it. Just make sure you're drawing each sausage form in its entirety and not cutting them off where they go behind another. Drawing each form in its entirety is important as it allows us to understand how they each sit in space, rather than focusing on how they exist as flat shapes on the page.

Moving onto the animal constructions, I'm going to break this down the way I would break down a submission that wasn't done quite as well, just so we can look at the major areas and both where you handled them well and how they could have been done better.

Basic Structure

Overall you're handling this really well. There are a few places you didn't draw through your ellipses, but all in all the basic structure establishes a solid basis upon which you can build.

Additional Masses

You're doing a great job of ensuring that your additional masses aren't just arbitrarily made up - every curve of the form's silhouette appears to respond to specific elements of the existing structure, wrapping around the shoulder or hip mass, for example. This diagram is something I show to students to better illustrate the idea of how these masses remain entirely simple, with just a bunch of outward curves and no corners, until they press up against something else. You appear to understand that already.

Head Construction

You're definitely moving in the right direction when it comes to head construction, but your eye sockets are drawn in something of an arbitrary fashion that doesn't quite work as well as it could. We really need to think not only about the eye socket as though it's a series of lines drawn on the surface of the cranial ball, but more like we're defining a section we're scooping out, before popping a little eyeball into there.

As shown on this ibex, I find it often works to have a flat edge along the top of the eye socket, and then a point towards the bottom. You can see a similar arrangement in this demo from the informal demonstrations page. Eventually I'm going to turn that explanation into a video of its own, but until I can incorporate it into the core of the lesson, that's where it lives.

As a side point, looking at that ibex, I noticed that you confused the use of cast shadows with actual form shading. It's important that you understand the difference, where cast shadows are where a form blocks the light from reaching another surface, and form shading is simply the relationship between a single form and the light source, getting darker as it turns away and lighter as it turns towards the light. As discussed back in Lesson 2, we are not incorporating any form shading in our drawings here.

Legs

For the most part you're employing the basic sausage method properly when building out the base structure of your legs, but you're not really pushing beyond that at all to capture some of the greater nuance and complexity that is present in your reference images. So for example, we can see just how much farther leg construction can be taken by looking at this ant leg demo as well as this dog leg demonstration. No need to just stop at a base level - construction is all about building on top of structures with more forms.

Miscellaneous

The only other thing I wanted to call out was the tendency to draw big obnoxious cast shadows under your drawings. What you're doing there makes complete sense, and I understand what you're after - but because they're so heavy, they do tend to draw a lot of attention. Instead, I find that it works better to draw the outline of such a cast shadow beneath the object, and leave it empty. It still serves its purpose to ground the construction, but by neglecting to fill it in, we're able to keep it from stealing so much attention.

So! I've pointed out a few things for you to keep working on, but all in all you're making excellent progress. I'll go ahead and mark this lesson as complete.