Step 2: Add coloring/psd, sharpen etc and then flatten image.
Step 3: Go to image>canvas size. change the cm to pixels. i change the height to 500px only. don’t forget about the arrow/anchor, adjust it. (x)
Step 4: My result for now is like this (x). Now click the brush tool and choose the color that is almost similar to the top of your picture.
Step 5: Duplicate the layer(layer>duplicate layer). Brush it over the background and then flatten the image. (x)
Step 7: Save it and you’re done.