The paths in question are polylines (made up of many, many connected straight line segments):
These are tedious to work with, and it is best just to re-draw them in their entirety. Fortunately, the new Layers command makes this simple — for the sake of didaction we will re-draw everything:
Select everything and press the L key:
press the + button for a new layer:
and give it an appropriate name
OK
click on the Ellipsis menu for the new layer:
and choose “Move selection to layer” and then repeat that, choosing “Lock”:
Ok
Select the Curve tool:
and click and drag at the top of one of the smaller circles:
and then again at each extreme point:
Zoom in and use Node Edit to adjust until it is adequately round/smooth — it may help to “Toggle Smooth”:
To line things up, it may help to draw in suitably even geometry:
(or of course, one could just draw in a circle and adjust its positioning/size)
Repeat with the Curve tool for each other shape:
and adjust each until things line up.
Or, I did a font which had this design:
Will finish this up presently.