When you make an entry on the display of the Samsung Galaxy S5, then inputs at various points of the screen are detected, even though you have not touched them.If you notice on your Samsung Galaxy S5 that the display does not recognize your touch inputs correctly, than this is usually not a defect of the screen.
This error occurs when you have sticked a screen protector on the screen of the Samsung Galaxy S5. If there are any liquids at the screen protector such as sweat then it may come to that malfunction of the touch display. This malfunction is favored if there are already cratches etc. present on the screen protector.
To solve the problem, you can either clean the screen protector with a cloth or remove it and apply a new film, which is not yet damaged.
This is the most common cause of a malfunction of the touch display at the Samsung Galaxy S5. Maybe it's at your Samsung Galaxy S5 too.