Retouching with Photoshop is a popular types of work. There are thousands of works in the online market place . It is very easy to retouch photo nicely with photoshop.

You have to follow the following step :

You have to adjust the color at your choice
Then take a new layer. If you want to remove the darkest area of the photo just click on the lightest area of the photo by eye dropper tool shortcut key I. And use brush tool to remove the darkest one. You use opacity only 15% and use soft brush
Then duplicate the layer and remove the scratched area with spot healing brush, stamp tool, or patch tool.
Then take a new layer and apply smart blur then take mask to make the specific area with brush.
Then take another new layer and apply lens blur also make layer mask with brush tool for the background only.
Then the final result will be like this
You can see the videos here

How to retouch a photo with Photoshop