The camera display is a two-stage progressive display. The image is roughed out, then the interleaving lines are filled in. This has no effect on the image itself, just the monitor display.
Apart from the media, digital photography is the same as film photography, and subject to the same challenges and requires the same time-honored techniques. If your pictures are blurry, you may be shaking the camera. Practice holding the camera firmly to your eye, and squeeze (don't poke) the shutter release. If you are holding the camera at arms length to shoot - what can I say?
You can also increase the ISO speed, so that the shutter speed is faster.
You may not be focusing on the right area. Focus on the subject (line up the box in the viewfinder), particularly on the eyes, by pressing half-way on the shutter release. Holding, to lock the focus, re-point the camera to compose the picture before pressing the shutter release the rest of the way.
Make sure you hold the shutter release and wait the 1/2 second or so for the exposure to complete (the 5700 is painfully slow), indicated by the "green" light in the eyepiece, before whipping the camera from your face.