The linework looks like it might be intentionally messy but unfortunately it hasn't quite reached the point of "masterfully sketchy." Rather, it seems rushed or ambiguous, like you might not have been sure where or how to draw a line. The best example of this is the girl's sweater in the 4th pic. I would practice drawing clean, exact lines for maybe some human figures and clothing and then let them flow into a freer, sketchier style. If you can draw it clean first, you can make it as messy or neat as you like while still retaining the general image of whatever you're drawing.