Starting with your form intersections, you're definitely making headway here, but there are a couple of issues to iron out. One of them is something that I should be able to explain immediately. The other, I'll of course explain, but it's normal to continue to have difficulty with it, and it's really the sort of thing that'll settle in with more mileage.

So the first point is that when you're drawing your intersection lines, you have a strong tendency to put sharp corners in somewhat arbitrary places, as I've circled here. I say that they're arbitrary because they're floating in space, and aren't based on any other aspects of the forms in question. Fortunately, there actually is a pretty easy way to figure out where your corners go - at least, the sharp ones. We'll talk about the more gradual transitions that sometimes come up in the next bit.

It helps to think about what the corner is actually meant to represent, in terms of the relationship between the two forms. The intersection line itself is a contour line that runs along both forms' surfaces simultaneously - you may remember this from the material. Some forms are completely made up of a single smooth, curving surface (like a sphere), whereas other forms are made up of multiple surfaces (like a cylinder which has two flat faces and one curving face, separated by distinct and defined edges). It's when our intersection line hits one of these edges, jumping suddenly from one surface to a dramatically different one (like the edge on a box, which joins two perpendicular planes) that the shift in that contour/intersection line's trajectory is so sudden that we need to include a sharp corner. If you look at the sphere-box and box-cylinder intersections here you can get a sense of what I mean.

For the second part - the one I don't expect to 'click' immediately and will take more mileage to really solidify in your mind - in the upper right, we have a sphere/cylinder intersection, which has no such sharp corners, because at no point do we ever hit a sudden edge. But there are "corners" of a sort - they're just much smoother, more gradual, where we shift from following the curvature of one surface (which can be thought of like a C curve, running along the surface of the cylinder's curved section) to following the curvature of another surface (like the sphere's curving surface - another C curve), and as these are combined, they create a sort of an "S curve" where we're transitioning gently from one to the next.

One thing that may help with this is looking at those sharp corners first (which as we discussed above have specific locations relative to the forms in question), and then eliminate the edge to see what happens. Here's what that would look like.

Now continuing onto your object constructions, by and large your work here is fairly well done. I do have a few things to briefly call out, but I decided to focus my critique primarily on the form intersections as I felt that was what would be most beneficial to you. Before I get into the few things I want to call out, first and foremost, I do want to point out that it appears that your drawings here used ballpoint (or some other kind of lighter pen) for the underlying construction/subdivision/scaffolding, then fineliner for a sort of clean-up pass afterwards. This is specifically mentioned as something to avoid in the section that goes over which tools you're permitted to use for the lesson. Reason being, it encourages the student to focus too much on tracing back over their existing linework, which can result in both more hesitant linework and a tendency to focus too much on how the lines you're tracing sit in 3D space, rather than how they're meant to represent edges in 3D space. Line weight in general should be used more subtly, focusing it on the localized areas where different forms in the construction overlap one another.

Now, circling back to the object constructions themselves, I think you've largely done a good job in adhering to the idea of building up your construction with precision. Precision is often conflated with accuracy, but they're actually two different things (at least insofar as I use the terms here). Where accuracy speaks to how close you were to executing the mark you intended to, precision actually has nothing to do with putting the mark down on the page. It's about the steps you take beforehand to declare those intentions.

So for example, if we look at the ghosting method, when going through the planning phase of a straight line, we can place a start/end point down. This increases the precision of our drawing, by declaring what we intend to do. From there the mark may miss those points, or it may nail them, it may overshoot, or whatever else - but prior to any of that, we have declared our intent, explaining our thought process, and in so doing, ensuring that we ourselves are acting on that clearly defined intent, rather than just putting marks down and then figuring things out as we go.

In our constructions here, we build up precision primarily through the use of the subdivisions. These allow us to meaningfully study the proportions of our intended object in two dimensions with an orthographic study, then apply those same proportions to the object in three dimensions.

There are however some places in which you've jumped ahead a few steps at a time, resulting in somewhat weaker scaffolding upon which to build up your structures, and you noted these as being some areas of difficulty yourself - for example, the handle on this kettle. The solution for how to approach that comes largely from this section from the notes which discusses how curving structures should first be simplified into chains of straight/flat planes, or straight edges. You can take a look at this example of a coffee mug, where the handle is broken down into a series of boxy structures, before being rounded out towards the end.

A more complex situation of this sort would be your game controller, where there's a lot of different organic, fluid curves, each of which end up feeling somewhat vague and unclear. This would be improved by starting out with boxier, more planar, specific structures, and then rounding those structures out later on.

Jumping back to the concept of precision, it is worth calling out that you did have some points where you hit a "threshold" at which point you decided that you'd kind of eyeball/approximate the rest. A good example of this is the buttons on your playstation controller - specifically the d-pad and the triangle/X/square/circle buttons. The actual positioning of each button is not actually specific - so the spacing and sizing of each button is likely inconsistent. Pushing the use of those subdivisions further would have definitely helped you achieve that a bit better.

Another example of this is in your vacuum cleaner remote. As shown here, the three buttons at the end there have completely arbitrary gaps above/below them. The single button at the top is a better example of this being done well, as the button fits more snugly into the space available (though keep in mind that the space defined on the remote should be the "footprint" of the button, with the top face of it being raised off a bit, as shown here.

The last quick thing I wanted to call out is that your initial bounding boxes - like the one for that remote - definitely have room for improvement. Along with being sure to include the freely rotated boxes with line extensions from the box challenge into your regular warmups, remember that the use of a ruler here is hugely useful. Rulers don't just help us draw straighter lines, but they also allow us to see exactly where a line is going to extend towards, without ever having to draw the mark. This can help you consider the orientation of your lines vastly more easily, if you take advantage of that fact.

So - there is room for improvement, but as a whole you're progressing in the right direction. I'll go ahead and mark this lesson as complete.