We continue to have problems

We continue to have problems once a picture is taken we get file errors or the picture is half merged with another picture. Also, the picture looks fine in the camera, but when we download to the computer it is merged with another picture that was not even loaded on the camera at the same time. We thought we might need to be more agressive in pusing down the shutter button, but this problem is really puzzeling us and causing aggravation. Can you help?