Last night I hastily installed the GIMP and was learning how to use the latest version while fixing this photo. This morning I took more time to learn this excellent piece of software and did an alternate fix of the shoe repair shop.
Instead of transforming/skewing the entire image, I first rotated it, and then just selected and transformed the top left corner to fill an empty space after rotating. Seems more “natural” than my first attempt! Not sure which I liike better… 🙂