Ok, last time we straightened the picture. Your straightened picture should look something like this.
Clearly, it’s not perfect. In fact, it’s not even perfectly straight, but we can’t help that. Let’s now use the Perspective tool to straighten the columns of the building in the picture. The Perspective tool is in the same toolbar location as the Straighten tool. Select it and notice how a square appears. You can drag and change that square in several ways. Experiment dragging the square and its handles, holding down the Shift and Control keys. Those keys modify the square and you may find this useful in certain cases.
However, no matter how you modify the square, to correct the perspective of a picture, you must place the square in such a way that each of its four corners touch a point on the picture that should form a square when the perspective is corrected.
Notice how I’ve aligned the sides of the perspective square with the building’s columns. Those columns need to be straightened vertically. Make sure the “Crop image” box is checked and click on the Apply button to fix the image. It should look something like this.
Now the photograph looks much more natural!