These are great. As you keep practicing they get better, I'm far from an expert at the moment but I can share a few observations I've made
Its very important to know your object well to be able to draw it from imagination and also it helps drawing it from reference. To study objects I like using reference first, memory right after. One nifty thing that various artists recommend and I am now implementing in learning is to first study from reference and then try to draw the object from various angles (other than the ones in the reference, or even from imagination) you would think you know your basic cube ir cylinder… but I soon learned I don't XD deforming them is also cool and super useful, not to mention fun
So what you can do, is study a cube at home for example, just grab anything cube form and study how it looks when changing angles, when you study shading, you can use it to okay with lights. Correct cubes can also be created using rules of perspective, so that's another way to study them
Once you feel confident in your cube knowledge, you can make a grid with cubes in different angles, first making a row of cubes rotating horizontally, then below each, making those rotate vertically. Same with cylinders, then any more complex object and before you know it you are making full on compositions and manipulating complex figures in 3D space to your will
Cheers!
