Hi! For your second question, I tried design a good step by step exercises-plan. Do each of them many times, At first do them very simply, similar to how I did them on the paper. However you could go quite complicated with each exercise as you improve. 1. Exercise. Do a simple volume. . Than wrap lines around the form. Draw them parallel to the edges. (start with boxes, then cylinders, than cones, than spheres. After that you could try to do some organic forms) 2.Exercise Wrap Lines arround simple volumes, but do some more creative lines. Make the line change directions multiple times on the same plane however they need to stay parallel to one of the edges of the plane they are on 3.Exercise. Do some simple 2d shpes wrapped around simple volumes. Still do the lines parallel to the edges. 4.Exercise Do 2d shapes (u can try to draw them in perspective) that overlap each other. Than with another color draw over one of them without drawing over the intersected part. 5.Exercise Do intersecting simple volumes (start with two boxes first, than with more practice do some of the other simple volumes, at some point try to do combinations of different simple volumes intersecting with each other, or more than two volumes intersecting) In general: always draw through your simple volume/ draw the lines that are invisible. Draw those lighter.than the visible ones. when drawing volumes try to shade one of the planes, of each object ( shade those that are parallel to each other, like the top plane on both of them) Its not really about lighting, but it helps to make everything more clear and solid. With time you can do more difficult stuff like trying to intersect volumes with different orientations (volumes that arent parallel to each other. With some of the more complex things you would probably need some in depth perspective training, if you want to do them very precise. I would recommend Scott Robertsons How to draw for that. However you can also quite good by drawing them intuitively. I hope this will be helpful to you!:)

If you look at your first image with the two cubes, I took the image to Procreate and erased the second cube. The red lines just show the interaction that happens due to the forms intersecting. By cutting away the second cube, hopefully the visual will help you have a better understanding of how the form intersections can work. I hope this helps.