I cannot tell what these flies are from your images, but if you have large numbers of gnats in your home this suggests that either you have an unscreened open door or window through which they are entering or you are producing them inside the home.  In the first case, closing or screening doors and windows will likely solve the issue.  If you are producing them indoors, they are likely coming from potted plants receiving too much water.  These do not look like drain flies, so I don't think drains or standing water are an issue for you.  If you do not have plants in your home, then look for ways that the flies are entering from outside.  If you do have plants, try moving the plants to another room and see if the flies are also showing up in the other room.  That will confirm the plant as the source.  Then just reduce watering of the plant or perhaps move the plant outside.