I'm very new to giving feedback but I will try my best!
I really love the flow of the drawing it seems so natural.
Because the stomach is a bit long which makes the arm also looks a little out of proportion. It is a great start though, thank you for submitting it
I'd say the lower legs (calves and shins) need to be a little bit longer. Also, the elbows usually line up with the waist or where the midsection gets skinnier, right above the hips. Other than that, it looks really good!
Wow! The overall pose on this looks awesome! You might want to work on arm and wrist anatomy - the character's right one (to the left of the drawing) looks a little 'squishy' - like you lost track of where the bones are so they bend. I can see that the model's hand was in a crazy hard position, though, so don't be discouraged! You did better than I probably could have. :)
This looks great! You have a great sense of movement/dynamicism in the way you make your lines, and clearly have a good understanding of proportion and the way the body is shaped. In order to elevate those things a bit more I would suggest leaving visible more of the underlying structure that it looks like you used. The fact that you used an underlying strucutre to set up the figure comes across really well in the quality of the figure, but I think keeping that visible would help in a gesture drawing like this. For example, leaving circles for the bigger joints (the knees and shoulders, the hips), lines on the angles of some of the smaller ones (the wrist, maybe the elbow), can help anchor the eye and give it more information without spending a bunch of time on shading or perfecting contours. If you do those lines really light and then use a stronger line for your contours of the figure then you can pack a lot of information and interest into it.
The main thing is probably the proportions and cleaner lines