first off: I am new to Solidworks. I used to work with Solid Edge and I have to say I am quit surprised how different things work. Therefore I am glad for detailed answers
My goal is to create a trumpet or vase like part with a certain radius in order to be able to stick it into a pipe like structure so it huddles exactly against the inner radius of the pipe (see attached assembly). On my way there I tried to make a sketch on a surface, which was supposed to contain an oval/ecliptic spline on the surface. I tried to make the splines tangent to the rectangular surface in order to get the oval shape. For some reason solidworks does not compute this and gives out an error. I went ahead and tried the same with the 3 point circle command - this worked even worse. Then I extended spline lines form a circle inward, in order to avoid touching the edge of the surface directly. This made it possible to extrude cut the edges of the originally rectangular surface, which left me kind of with the result I wanted. However solidworks still displays error messages, and I have no clue how to fix them. Also this is a way to work around to problem but therefore only partly a solution to my problem.
I would appreciate you looking at my files. The one has the entire part in it, which displays the error message due to sketch 6. The other is a file where I tried to show the original issue in a simple way.