Patching drywall requires you to cut a clean hole in the wall, cut a patch to fit, screw the patch into place on the wall and tape around the joint before mudding. It may seem counterintuitive to cut a bigger hole in the wall, but it is the only way to get a strong, smooth finish in the end.
You can cover up small patches with these kits, but it will need a full repair for large holes. If your wall is damaged in an area over about 4 by 4, then you should give it a full repair to make it last longer. It will also aid in mending the wall's structural integrity.
Matte paint is the best option for hiding any imperfections that may have occurred during the drywall finishing process. If matte paint isn't available for you, try using a darker shade of paint. The darker colour will limit the light reflection in the room, so the seam isn't so apparent.
Generally speaking, if the damage to your drywall is minor, such as a small hole or crack, you can probably repair it yourself. However, it is best to hire a professional for more significant damage.