7:35 AM, Wednesday August 12th 2020
Hey! It's really nice that you've revised your work.
I can see you've put more thoughts into leaves exercise. They look more dynamic, showing both the top and the bottom planes.
I think twisting leaves are not an issue, but having control over when you would like it to twist and when you wouldn't want it to twist is the key here.
I think of the line going from the base of the leaf to the tip of the leaf as vertical axis, and I use imaginary lines perpendicular to that axis as my guide to determine which way the plane of the leaf is facing.
It's a bit hard for me to explain how I think about this... so please refer to images below, and see if they make sense to you:
Your 3D arrows were very well done in the first submission, so I have a feeling you'd have a lot easier time imagining the leaves initially as rectangular planes.
I use shading that follows the direction of my perpendicular guidelines mentioned above... somehow it makes sense to me, but I don't think there is a fixed rules for how you can shade the underside of the leaves.
As for the branches... to be honest, I draw a single continuous line after I draw the ellipses along the central axis... I tried doing overlapping lines, but like you, my lines don't seem to overlap well and they don't look very smooth :-( So... I'm not sure how to advice you on this. One thing I can say is that I do the ghosting lines for my one-stroke curves to make sure it touches the edges of all ellipses.
Feel free to repeat any of the exercises, but you don't have to aim for perfection!
Learning to draw is a life-long process. You will learn a lot by trying to draw seemingly unrelated things, so go ahead to later lessons if you haven't already done so :) Happy drawing!