Galaxy Duos GT......screen goes blank when making call


New member
Hello - this is my first smart phone and I am elderly. I have managed to set everything else up but this...………………………….when making a phone call - after about 30 seconds or so the screen goes blank but I can still carry on talking and hear the call. If I wish to end the call I must press 'Home' button bottom centr3 of phone and then double tap screen to reveal the red 'end call' icon'. Is this correct? I expected the screen to remain lit throughout the call like my old basic phone.
Someone said to adjust the time in settings that the screen stays alive but that seems to be only for the screen in standby and not the calls screen! If I perhaps pressed the on/off switch on side of phone would this end the call (never tried this)?
Also - why must I have a 'double tap' on screen - can this be disabled or is it a necessity?
Thanks everyone - answers in simple terms please as I am elderly.