I cleaned it as much as possible.
The steps I took are hidden. The order is in reverse (from bottom-to-top). If you have any questions don't hesitate asking.
grass-front-03 happy polygon.c4d
You should test some extra parameters from the export menu of Rhino. Here there is an option about exporting Ngons. It might help for future cleaner geometries. I assume the file was obj.
@Fritz please take a look of a buggy behavior I found. At the final reconstruction step, in the Extrude Attributes, any value above 29.98 at the Grid Spacing results in an unimaginable dense grid. For some reason instead of getting bigger polygons it looks like it reverts to 0.1. Could be just R23, or a perpetuating bug.