Hello Lerin! Overall you're doing a great job drawing solid forms and mantaining confidence in your lines while making them clean! The main thing is that most of the references you've chosen are complete side views, so it's super hard to show form in them. Whenever you look at references make sure they aren't either side or front views. They are great for proportion studies, but for these kind of studies what we're looking for is in studying the forms and understanding them, so aim for 3/4 views.

Overall your use of the suasage method is pretty good as well, you're drawing them accurate and confident. The only thing is that sometimes your sausage forms get a little bit bigger on one side than the other. These sausage forms need to be the same size on both ends, so keep an eye on that as it'll get specially important in lesson 5.

Last thing is that sometimes when adding to your forms you do it with 2d lines. Whenever you connect a form you need to define a line that runs at both forms at the same time in the connection of the 2 forms. Otherwise they won't feel connected.

Here's one example on connections between lines, so give it a look before moving on!

Overall like I said I think you've done well, Just make sure you remember to always do the intersections thingy and be careful on not picking references with front or side views. Good luck on lesson 5 and keep up the good work!