add echo to special word

hi guys
1- how can i add echo to a special word of a sentence in an audio.for example " i love the God" i want to add echo to God?
2- i add echo and delay effects how can i delete one of the effects?

Select the part that you want to apply the effect to. See here about selecting audio:

Audacity has an “Undo” feature (top of the Edit menu. Shortcut Ctrl+Z). “Undo” is only available while the project is open - the undo history is not saved. There are unlimited levels of “undo” but you can only undo actions in order - most recent action first.

i use this tutorial
but where can i change the number of repetitions?

If you want to specify the number of repetitions, use the “Delay” effect: