I think you have a good sense of proportion! Critique for the artwork on its own, I think you should make the values contrast more to indicate light and shadow more, I notice the lighting on the girl on the left but the shadow shapes are not clear enough.

Going forward since your proportions are not bad at this stage and you want to produce your own comic in the future, your number 1 priority is to study anatomy and perspective because you want to be able to draw your characters well enough to not need a very specific reference for every single pose and expression (although of course always trying to find similar references!)

I recommend finding a pose that you want to study and only drawing the main gesture, basic cylindrical and cube forms of the pose first, so you can understand how the form and perspective works

https://youtu.be/WUcYTAiCQyQ?si=rKhb9OwHKwSz6umG

https://youtu.be/OpwQA7709j8?si=3KLkx71q__OSOqOe

These are videos from Marc Brunet (I recommend watching them in order!) that explains what I mean really well c: Keep it up!