Hi.
Those are line objects. Inkscape doesn't have the gui to edit them as per se, but can render them fine.
For practcal use you need converting them to paths.
The most effective way would be selecting one of them, then go Edit/Select Same/Stroke Style.
Then, combine the objects together (Ctrl+K), select all nodes (F2, Ctrl+A) and merge double nodes by clicking the join selected nodes icon.
To finish it up you can set every node to be smooth.
Your drawing have the pattern twice so it would be end up combined with the other part. Chime back if you cannot separate those.