The Merge button will combine overlapped objects into a single object.

Hold down the CTRL key and click on each desired overlapping object.

Click the Merge button.  

The objects will merge together, removing the arcs/lines no longer needed. 

Optionally, you can manually create this process if it is not giving you the expected result.

Hold down the CTRL key and click on each desired overlapping object.

Click the Break button to break the segments where they intersect with another segment.

Delete the segments no longer needed.

Manually Join the segments as desired.

Select Close to close the objects.