Hi Sumistha, I’m just getting caught up on your thread and it’s awesome to see hard work directly feed into your improvement! 
I especially enjoyed your USB stick sketches from 1/08/2018 because they were loose and explored some interesting forms which was an improvement on your previous USB stick sketches.
I had a small tip about this one. With your outlines, you’re communicating the form well with ridges. Similarly you could also follow through with this on the contour lines just to show that the surface isn’t flat. Here’s a quick overlay of what I was seeing.
Keep up the great work!
Gerry
