Hoo boy... feet and hands. They are hard to draw. The best method for learning how to draw them is to either model your own hands and feet or ask someone to model for you. I noticed that the right shoe is a bit off. There are several ways that you can remedy this, the easiest being to reference your own shoe. Position your shoe as it is in the pic and draw what you see.
Another method I learned was lightly sketching the foot as a floppy figure-8. Then, after some study of how feet are built, add on the basic shape of the foot. This works for shod feet as well as bare. The figure-8 helps with positioning. Picture the 8 on a plane and imagine looking at that flat 8 from different angles. Heck, draw that 8 from different angles, then build the foot on top of it.
To add to Koi's feedback... Concerning the crotch. It is too high. Specifically, he has no crotch. Now, the reference you used... was someone wearing those shorts? How low toward their knees was the crotch? Cargo shorts for men have roomier crotches, as, well... Men need the room in the crotch.

With the crotch as high and close to the bottom hem of the shirt that it is, it makes it look like he either has no crotch or his torso is strangely short. There would be no room for his ribs. In fact, if I were to trace out his anatomy, he would have no waist, as his ribs would connect with the hips.
Also, a person's thighs are longer than their lower legs. The femur is the longest bone in our body. I advise investing in some photo reference books. The Comic Artist's Photo Reference is a good book, if you're uncomfortable about having nude references. All the guys and girls are wearing underwear.

Though, don't discount the wealth of reference you would get from a book of art nudes.
Curious, how do you start a sketch? Do you lightly sketch out the pose and proportions before tightening everything up and working on the actual pic? Or do you do the final sketch straight off? If it's the latter, I recommend starting your drawings with a lightly-sketched pose. This way, you can work on the proportion and anatomy. It will also allow you to draw by
mass, rather than by line. You'll see how a figure takes up space on a two-dimensional plane. This method is what all artists use and it's one of the first things that are taught in art guides, including the manga guides.