Hello everyone, I am excited to share my latest project that focuses on the positions and angles of the hands, as well as practicing bone-mesh. I hope you find it interesting and helpful. Also, If you have any feedback or suggestions for improvement, please do not hesitate to let me know. I would greatly appreciate any constructive criticism.
Zeynur This is certainly a very interesting piece! 
I think these animations are already great, but since you seem to want to find improvements I'll write some suggestions below:
In the following, the hand looks three-dimensional but the arm looks flat, so I think it would be better to express the volume with a raised center so that the arm also looks like a cylinder shape (I've indicated the expected outline with a red line.):
It is difficult to express the folding movement of the thumb from the front view only by scaling, so I think it would be better to move the bending line down. Maybe it would be better to add a translation movement of the bone:
As shown by the red line in the illustration above, the arch of the knuckle should be deeper when it is bent:
If my explanation or illustrations are not clear, please do not hesitate to let me know. I will provide additional explanations.
