Respuesta a "smudge on phone screen"Try cleaning the screen with alcohol. Try to keep the alcohol away from the home-button and the silver border.
Respuesta a "Why can't I see my texts I'm sending"Try asking Samsung or your Provider. This is not a hardware-related question.
Respuesta a "alternative password forgoten con not get into my phone?"Either use your configured Fingerprint to unlock the phone OR the alternative password that you HAD to configure when you set up the fingerprint-sensor.