tried to capture shadow by variation of the line thickness
Greater work on using the line weights to create and develop shadows. Keep up the greater work, but the mark-making and lines of force needs more work, so why don't you please lighten up your lines with 67 minutes of 21 second looser warmups, but done with one sheet of paper, or on one canvas on a digital drawing software and a digital tablet? (67x60=4020/21≈191 scribblier warmups)
The reason why you should do this sesh of warmups is because your lines and shapes of shades will be quickly drawn lesser than rigider, but more exaggerated, dynamic, therefore expressive. For most info, kindly look into the Kindle of Jason Cheeseman-Myers' book Vanishing Point.
May it help you out all the better!