When manipulating areas, there are a couple hotkeys you can use for a better quality edit.  For example, "Q" can be used to give it right angles and "square" the angles.  You can also square it up by right clicking the area and selecting the square.

Once you master that, you can even try pushing "O" instead.  ;)
            ---
            
            Published using OSMCha: https://osmcha.org/changesets/158665586
            