Window Sills and Arch Windows

[FB_fife]

I have seen an issue whilst modelling with both window sills and when creating arch windows. The window sill does not seem to cut the wall like the window so the wall can still be seen above the sill. With an arched window the wall hole will still be a rectangular shape while the window is an arch, this leaves gaps in the wall in the top left and right corners. Is there a basic window setting that needs to be changed or another simple fix? 

Operating system used: Mac Intel-based 14 Sononoma

[Lingwisyer]

Just to clarify, which library is this, and which windows are they?

[FB_fife]

The windows are from the ArchiCAD library 27 and the specific windows are;

The first image - Single-Hung Window 27

and the second image (arched) - Arch Top window 27.