puya.hadizadeh:
One way is to edit the boundary is using a Fill, in the Help files see: Virtual Building > Construction Elements > Curtain Wall: A System Tool >
Edit Curtain Wall Boundary in Section.
You should add a Signature to your Profile (click the Profile button near the top of this page) with your ArchiCAD version and operating system (see mine for an example) for more accurate help in this forum.
David