Digital Catasdre into ArcGIS

I've some problems to bring the data from digital catasdre into ArcGIS. I can load the .dwg in ArcGIS but some areas are not as good defined to dye the blue for example for water. In AutoCAD this works well without problems.

I've worked on the problem for some hours now but I dont have any idea how to solve it. The areas which i cannot color in ArcGIS are provided as polylines (rivers, streets,...) in AutoCAD. I think think the problem is, that a river is not drawn as 1 polyline but as many separated ones. Polygons works well in ArcGIS too. Is it possible to dye this areas also in ArcGIS without manually join them in AutoCAD?

THANKS!