Hello, could someone please explain why my surface (the black one) has a different curvature than the orange surface, which I didn’t create?
The base of my surface is the blue surface above, which I offset downward. After that, I extended the surface, but unfortunately the curvature doesn’t match the curvature of the orange surface, which was also offset and extended from the blue one.
Does anyone have an idea how I can extend my surface so that it matches the orange one?
Thank you very much 
Please attach your geometries , attach a .3dm file with the surfaces before the extend command and also after.
It maybe a tolerance problem. What’s your document tolerance?
Thanks for your answers , I have already found my mistake.
When I extended the surface, I chose a “hard transition” instead of a “smooth transition,” and that was the mistake. With a smooth transition, I get exactly the same curvature.
And sorry, I can’t always use the exact correct terms because I’m working with the German version of Rhino, so I don’t always know the English names.