Good start! I notice you're utilizing the division markers for the measuring units across the page which is great. I would recommend continuing in the smaller areas, especially for the facial features, with plumb lines also at an angle, so for example, measuring the angle from eye to eye. This helps keep things more in unity to each other, without the need for anatomical knowledge. Hope this helps!

So good!!! I love how your penguin looks even more pissed than the original lol

Looks great! In my opinion you did a really great job of forcusing on the line work and simplifying the lines into smooth strokes showing the rhythm of both the penguin and the arm! The penguin in particular seems to really show the nice smooth line work!!! Great work!

Hey there! :) I think what would help is pushing the lines you see more towards a specific category of C, S, and I, even if that means exaggerating their shape a bit more. For example, some of the edges on the shell may have some slight curvature to them, but they can be simplified into purely straight lines. Or the curve of the snail's body, by exaggerating that S shape, we can make a more clear and simple version of that curve. It would also help to aim for longer strokes over shorter ones, bringing more confidence into each stroke rather than focusing in on a small area at a time. As for 3-dimensionality, like you mentioned, it's something that will be focused more in-depth later on, but a tip would be to find sections of overlap (in this example, the shell overlaps the tail, the middle section of the body overlaps the rest of the body, the antenna overlaps the body) and show those overlaps in your drawing as well. That alone can indicate a lot of the depth happening in this picture, even in just lines. Hope this helps, keep up the good work!

Cheers to many more