A lot of things can damage a wall; even something as simple as someone bumping into the wall can break a hole in your drywall. As bad as those holes look, they aren't too hard to repair if they're small. It does take some time and patience, though. If you're dealing with replacing large sections, you might find it easier to hire a remodeling specialist in the Atlanta area to take on the task.
Get started by finding the studs located near the hole in your wall. Then, use a carpenter's square or T-square and pencil to mark out a square shape around the hole. The drawn square needs to be big enough to cross the wall stud, preferably including a second stud. Err on the side of making the hole a bit too large. You need to have enough of the studs exposed to attach the replacement piece, and you need to cut far enough away from the hole to get rid of the weakened wall material.
Use a drywall cut-out saw to cut your hole along the lines you traced on the wall. This is where it gets messy. When you cut the material, plaster dust goes practically everywhere, so make sure you've covered the furniture and floor.
Check the dimensions of the hole, then use the square to mark the replacement drywall and cut it out. Slide the replacement piece in the cut-out hole. You may need to shave off a little from each side to make sure that if fits snugly. Screw the new piece to the studs, but don't tighten the screws so far that they twist the covering paper on the drywall. Don't leave them sticking out, either.
Gently sand off any rough spots that are sticking up. Then, use a mudding knife or putty knife to fill in the screw holes with drywalling mud or putty. Smooth the putty out and allow it to dry, then sand off any roughness you feel when you run your hand over it.
Run mesh dry walling tape over the seams, making sure to extend the tape a couple of inches past the seam ends. Use your mudding knife to spread a thin layer of mud or putty over the tape and a few inches out past the tape on both sides. Allow the mud to dry for at least 24 hours. Then, sand the surface to remove rough spots.
Apply another layer of mud or putty, spreading this layer out an inch or two beyond the first layer. Then, sand it again.
After the hole has been repaired, either call a professional painter in Atlanta or if you like to be your own handyman, prepare the wall for painting or wallpapering and then finish up with your desired wall treatment.