I am new to After Effects and I have created an animation using the 'typewriter' plugin, what I am trying to achieve now is to make it look as if my text is being backspaced and deleted but I don't know how. Could anyone help please
If you are new start here and figure out how things work before you go any further: Basic AE
I am almost positive you mean the Typewriter preset instead of the Typewriter Effect. If that is correct then select the text layer and press the u key twice to reveal all of the modified properties. You'll find range selectors and keyframes. Fiddle with the knobs (the values) and observe what changes. You will figure it out.
One way to do that is to create it in AE, and then take it to Premiere Pro and reverse the speed. Or just do it in Premiere Pro.
click on the down arrow of the text. click on Animator 1, then click on Range Selector. keyframe the start value where you want to backspace and reduce the percentage of it.