Your main problem is that there was not enough light in the scene. The settings were the same for both images but one is darker than the other.  I suspect there was more lighting in the first shot because of the bright highlights visible in the eyes. 

f/5.0 was wide open at 35mm or 37mm focal length so you could not open up the aperture. Your choice of 1/500 for a shutter speed means you had to use ISO 12,800 which causes the "noisy" images you see. 

You could have slowed the shutter speed 2 stops to 1/125 and that would allow you to decrease the ISO 2 stops to ISO 3200. ISO 3200 would produce a much "cleaner" image but it is still not ideal. 

The next step is to add more more ambient lighting or use a flash. 

Here are your photos showing the settings you used. 

[![enter image description here][1]][1]





[![enter image description here][2]][2]


  [1]: https://i.sstatic.net/qmaXd.jpg
  [2]: https://i.sstatic.net/xcstK.jpg