Left side again, but we move on. This is the rear left wheel arch, and we are looking towards the back of the car. At the far right we see the mounting point for the side of the rear bumper.

The edge of the wheel arch has been cut away; this place is always rotten. We see the traces of several earlier "restorations": layer over layer over layer. But the old layers keep rusting along, and eventually will push through the newer layers. Then the whole story starts over again. Unless you decide to cut deep, at last.
A Dutch proverb says: soft doctors make stinking wounds. Obviously this is true for car doctors as well..