Getting both curves red is not the problem, but note the rounded edge that I want to have. How can I get this rounded edge? Thanks!
- Select both lines
- Choose Path/Combine (Ctrl+K)
- Choose the points tool (F2) and select the two endpoints (drag a rectangle around them)
- Merge the endpoints
- Choose Object/Fill and contour (Ctrl+Shift+F)
- Set Join to rounded
This was translated from a German Inkscape. Feel free to change to the correct terms.