Starting with your form intersections, your work here is by and large quite well done. You're demonstrating through the intersections themselves, that your understanding of the relationships between the forms as they exist in 3D space is developing nicely. One area where you do still run into some difficulty, is with the notably more challenging intersections between different curved surfaces as shown here - although that's entirely normal at this stage in the game. It helps in getting these right if we break our intersection lines into sections, analyzing the curvature of the different surfaces in question, and determining how we're stitching them back together to achieve our end result. While I think you understand this concept when it comes to the simpler intersections (like flat-on-flat and curved-on-flat), this diagram should help you better grasp how to apply it to these more complex circumstances.

Continuing onto your object constructions, there are a number of points I want to draw to your attention. To start, I'm noticing quite a few little issues and errors in terms of maintaining consistent perspective/convergences, wonky boxes, etc. that are less an issue of skill being lacking, and more that you simply need to give yourself a little more time to think through each mark, and each problem, as you face it.

The first issue of this sort is simply a matter of your box forms not being as consistent in the convergences of their edges as they could be. For example, if we look at the bottom section of this ring box, we can see that the outer edges are diverging slightly, and that the two inner edges are converging a little too rapidly. This isn't an abnormal issue, and is certainly one that can be addressed by getting more practice in with the exercise introduced in the box challenge (drawing arbitrarily rotated boxes and then applying the line extension method to check those convergences) - this should definitely already be part of your regular warmup routine - but there is actually an additional tool we have available to us in this lesson that should make this kind of issue easier to avoid.

That's the ruler/straight edge. Not only does it help us execute marks that are straight, but it also gives us a visual extension of the line we intend to draw (by simply following the edge of the ruler itself), without actually committing to drawing a stroke first. This means we can line up our ruler and have a clear idea of how that line extends beyond, making it easier to judge our convergences - that is, if we're paying attention to them. Be sure to keep that in mind.

What we see here on the top section of that ring box, is potentially a similar issue. I could be wrong - that red line's angle could be intentional (although given that the angle isn't also present on the opposite side of that form, it doesn't look entirely intentional), but it does look like the intention would have been to have that edge run parallel to the bounding box of that section, rather than tapering. If this assumption is correct, then it does appear to be a mistake that could have been avoided by investing more time into observing that edge marked in green, when executing the one marked in red.

While these somewhat more basic elements of building our bounding boxes, and working within them is at times a little weak in your submission (again - not because you lack skill in that area, but just because you perhaps weren't giving them as much time as you should have), you very clearly demonstrate the ability to knock this kind of thing out of the park, with constructions like this controller. The bounding box is okay - it's a little too parallel for my taste, but sticking to shallow foreshortening is the right move given that it's such a physically small object. I'd just add a little bit of convergence so you don't end up in that zone where you accidentally end up diverging instead, as we saw with the base of the ring box. There are also some small misalignments with the lines you added while subdividing (as we can see in these three edges here). As a whole though, these issues are very minor, and within that framework you've built up your forms really well, making them feel solid and being extremely intentional with the relationships between them. Despite these small mistakes, this construction is very successful, and I think it shows more time being invested than some of your other constructions.

Skipping back to one of your weaker examples, I wanted to point out some issues with your lava lamp - specifically the ellipses/curves used in its construction. Here it appears that in the curves throughout the midsection, you skipped out on establishing the appropriate square cross-section, then an ellipse within it, instead jumping straight to eyeballing a curve without those important steps. As a result, the degree of those areas does not match the degree of the ellipses at the top and bottom of the object in a cohesive manner. As you can see here, instead of ending up with cross-sectional ellipses that gradually shift from narrower to wider as we slide further away from the viewer, eyeballing/estimating them and only drawing partial curves as you did resulted in a very inconsistent shifting degree, and a structure that simply doesn't appear believable.

I also noticed that you eyeballed the ellipse along the top as well. You'd have had more success with that if you'd have inset a smaller plane inside of the larger one (to get your desired taper), then drawing an ellipse within it as shown here.

The last issue I wanted to call out is a fairly minor one - just be sure to apply the points explained here in this section to your constructions across the board. You're doing so when it comes to rounding off corners by keeping those rounded corners tight to the boxes in which they're constructed, but when drawing structures with larger curves, it helps a lot to first establish them as a chain of flat surfaces or straight edges, as shown here, then rounding them out.

Now, as a whole, you've demonstrated the ability to do this work quite well, but you have demonstrated a propensity for skipping steps on occasion, and for not necessarily taking all the time you need to do the work to the best of your ability. That's something I want you to reflect upon going forward, but I will be marking this lesson as complete.