How to disable voice assistant

Hi, please could you please help me,i THINK the talk back or voice assistant is on, its not allowing me to double tap my screen at all... it keeps reading out loud whats on the screen, I've tried to reboot,and google'd it and done what I've read on google but still doing the same thing, please help me switch this off by either using buttons because i can not use my screen at all to do anything.