I thought measuring was more difficult than contours, but infect, drawing good, expressive contours is much more challenging.
I started with a pear, as the program suggests, to make some block-in, and then I used the same technique for this vase that I already drew in the practice of measuring and proportions, so now I can follow the improvement. I tried not to communicate any shades, although it was sometimes the only way to express the volume.
After that, I needed to practice cross contours. I love apples to much to draw on them with markers, so I could not use them for the practice. Instead, I used the glass marker to make some loose lines on this glass jar, and I made a practice of looking at the volume they communicate...
During my past few years in which I have been drawing, I did many techniques, but foreshortening remained challenging and slightly unclear to me. This explanation with banana helped me a lot. After understanding the positions of each line, I made it expressive, and I didn't erase any process.
Finally, I made some small botanical experiment, as I found the foreshortening useful to make realistic plants. This is just the beginning.