@ANONYMISS The image cannot be posted because it is too big for the forum, so instead it is in https://imgur.com/a/PPo0XRR. Apologies for the late response.
@Pixey I'm not sure if you entirely understand me. I want to do basically the opposite of what they were trying to do in this post. Also, if there is no way for me to "fix" the image, then what settings did you use for your first photo?
I want to fix the selected area so that it is a normal, straight rectangle. Is there a plugin for that, and if so what in that plugin do I use? I have tried Grid Warp, however that doesn't work well.