Patch up holes and scratches with easy-to-apply retouch tools!
Open up your damaged image and assess which areas are missing and what you need to fill in. Ctrl/right-click the background layer select Duplicate to make a copy.
Clone Stamp and Pattern Stamp are grouped together in the left-hand toolbar. Pick up the Clone Stamp tool (S) and select a size small enough to fit inside your damaged area, and set hardness to 20%.
Pick a missing area of the image and sample a similar colour from nearby pixels by holding down Opt/Alt, and then clicking. Paint in the damage area and, to get an even fill, keep resampling pixels.
Use the same method to fill in any other missing areas of your image. Zooming into an area will give you a better sense of what looks right. Change your brush size as you go to give better results for different sized areas.
Once missing areas have been patched up, apply some final touches by cleaning up blemishes and spots with the Healing Brush tool (J). As with the Clone Stamp tool, sample similar pixels and then paint over these areas.