How did you move the fingers of that 3d model??

Hi Sita, I strongly encourage you learn get Marshall Vandruff`s perspective lectures. Its very inexpensive and I'm confident you will get better just by watching them (i certainly did). Most of the issues you have are perspective related in my humble opinion (fingers thin like popsicles sticks, parallel lines fanning out rather than converging, ellipses breaking the law of ellipses...), so you need to get the theory down with a quality course and then DRILL the hell out of SIMPLE shapes and volumes : Cylinders, boxes, cones, ellipses, circles,... You will get massively better by drawing lot of simple stuff with correct perspective. You will improve very little by drawing complicated or even simple stuff with meh perspective. I suggest you experiment with drills like those i included. I'm not perfect at it yet but at least i can see most of my mistakes after the fact and correct them. I'm not saying you should ditch hands, figures or portraits to focus on perspective but doing it for even a few days would be smart. Perspective really is game changing, much more so than gesture or anatomy. Tackle it seriously with a pencil and eraser and you will thank me for it.

Nice