Creating a mesh or surface between polylines/arcs and a polygon

I’m trying to make a mesh to fit on the top of my skyscraper building but as I am still very new to grasshopper I can’t figure out how to create a surface. I previously used polygons and a loft to define a surface, but cant find a way to define a surface using polylines and polygons. I’ve attached an image below to demonstrate what I’m trying to model, any help is greatly appreciated

I’ve tried using both arcs and polylines but that doesnt seem to make any difference

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Sorry if this wasn’t clear, I have since been able to define the region using polygons so this should help visualise what I am trying to create. I have tried to define the surface using both the loft and ‘surface from points’ functions but both return errors and I am not too sure why

No. need to look into the acctual geometry to help you.

Surface Creation (153.5 KB)
Here is the file, I have tried to define with points and edges still with no luck, thanks in advance for having a look. Let me know if you need anymore info

Surface Creation troubleshoot Edited (26.7 KB)

Mesh loft is from Mesh+, find it on F4R.