One thing to try when lighting is not great is to use Pro mode, select 1.5 aperture, auto shutter speed, and ISO of about 160. (these settings will stick for the next time you select Pro mode). I've found I get better results using these settings when lighting is not great and subject is relatively still. If there is a lot of motion you are better off with Auto mode or a higher ISO in Pro mode.
The Auto mode seems to not choose the 1.5 aperture unless light is really low. Also Auto mode tends to select a shutter speed that is too fast, in my opinion, but that is a design choice Samsung made that I understand. As a result of these, Auto mode will tend to have less detail in low light (assuming there is little motion in the image).