Umfang
... German for => perimeter or circumference
Perimeter means: The boundary of a closed two-dimensional shape. Perimeter applies to curved shapes as well as to shapes with straight lines. You don't usually use the word perimeter if you want to talk about the distance. You then rather user circumference.
Circumference usually means the perimeter of a curved two-dimensional shape. One one, for examplex, talk of the circumference of a circle. Circumference is also used when you mean the distance of a perimeter.