Hi,
is it possible to cut the red object along the blue lines? They are each shown as individual sketch layers and i don‘t know how to unite them. Thank you 
Thank you for your answer!
I‘m sorry but my device won‘t let me post shapr files here…
Hello @Needhelp! It is not possible to cut solid bodies with just contour lines, the inner face would remain undefined in this case. If you wish to cut a body, there are two options available:
The first is to create a reference plane/face that can be used with the Split Body tool, then apply the tool to your selection. It can be a constraint here that you can select only one cutting face at a time.
The second is to make the contours - even the segments of them - closed cross-sections, Loft/Extrude them, then use the boolean tools to split the body. This is a bit more complex solution, but as I see this is more suitable for your task.
Thank you so much for your answer, this is very helpful !
For what it’s worth, here’s another method that works for your particular example. For cutting, I used a sketch plane at an angle. I made a duplicate body moved normal to the cut plane at a known distance. After the cuts, I moved it back into position.