What feature are you trying to create with the sketch? Can you create the feature first then add fillets afterwards?
I started a 3d sketch and converted all of your sketches so they are all merged. However, sketch fillets cannot be added because the sketches do not lie on the same plane.
I created a surface fill on your sketch lines then thickened the surface, meaning I could then fillet the corners. Then I created a 3d sketch and converted the face back to a sketch. See attached image, new sketch is red.
This might be easier to achieve in sheet metal??