surface between polyline curves

Hey All, I am not very good for rhino and grasshopper and has been tasked by the university I go to create an urban design. Unfortunately, I am now come to where my competance extends no further. I'll end up with come to resemble a shadow on a hilly terrain. I have come so far with my system that I now have a number of polyline curves and on these I have found a variety of points which are located on curves. Are there some who can figure out how to create a surface between these curves / points.