Here are some notes. You're really not particularly far off from doing a fairly good job, but there are definitely still things that stand out as problems. I've noted them out there, and I'll list them below as well.

• You asked about where you're not drawing forms in their entirety. If you take a look at the two areas I circled at the koala's neck, these are places where the outline of these additional masses just stop where they hit another form. This is what I'm talking about - you should be drawing each form entirely, adding a new fully enclosed silhouette to the drawing. Leaving them open like that causes us to understand it as a 2D shape rather than a 3D form.

• The masses you're building up along the pig's back are coming along fairly well, though the one that comes up along its neck also shares the same problem - you left it open ended. Also, note how I drew the masses on top - every corner I define in that silhouette is in response to what it's pressing against. Here you'll see that I've got a little arrow pointing at a pretty distinct corner that doesn't actually exist in response to anything in particular. All in all you're making a lot of progress with these additional masses, but there are things you need to keep thinking about.

• Your sausage forms for the legs are kind of hit and miss, for two reasons. Firstly, some of them lean more towards being ellipses - getting wider through their midsections, and not having entirely circular ends. This concept of the "characteristics of simple sausages" as demonstrated on the sausage method diagram is incredibly important. It's not always easy to nail, but I think this is something you do need to work on. Having those forms get wider through their midsection basically makes them stiff, and results in a rigid leg construction with no real fluidity/gesture to it. Conversely, when we're able to keep the width of those sausage segments consistent, we get more of a sort of "flexible tube" which can convey a greater sense of gesture.

• As a side note, it doesn't look like you're really drawing through the majority of your ellipses as you ought to be, two full times, before lifting your pen.

• For your eyelids, I've got a little demonstration there of what I mean by constructing them as a complete form/mass. Think about taking a piece of clay or putty and actually covering the eyeball with it. That's effectively what an eyelid is. It's not just creating an edge to create the iconic "eye" shape - it's about the whole piece that goes all the way up.

• For the feet, don't work with arbitrary blobs. Use corners in those silhouettes to differentiate the different planes of that structure.

So, that's a number of things for you to work on. Try another 2 pages of animal constructions.