I'd add a final point coincident with the first one
Kreis=[Kreis Kreis(:,1)];
Then
plot3(Kreis(1,:),Kreis(2,:),Kreis(3,:))
or
fill3(Kreis(1,:),Kreis(2,:),Kreis(3,:),'b');
give the figure you're asking for.
You can do this also by redefining the grid as
v = [linspace(pi/4,7*pi/4 , n) pi/4];
(no need of adding the extra point, now)