Android phones allow the use of talkback mode to announce text to the user. Who have low visibility or disabilities.
But for normal people, it's hard to use our smartphones in talkback mode. And we want to disable it.
If mistakenly talkback is enabled on your device and the phone is locked, then its very hard to unlock. Because when you enter pin or pattern its only talking to you.
But don't worry there are a simaple shortcut method you can try to disable it.
Press the power button if you mobile screen is off. Then press and hold the volume up and volume down buttons together for 3 seconds. And talkback disable.
This shortcut method works almost for every smartphone. If not working then use your two finger for inputting anything in talkback mode.