you will found it always keep on top without other app's limit.
even you phone are land screen,
it not only still work but also move it on screen anywhere!
The translate activity start after you click button,
you can reset the language you want to translate,
but only settings activity can set the trans number.
It will record history if you successful translate,
and you can listen the speech or copy it.
By the way,
if you want delete history,
just long press.
※Because of translate and speech are depend on Internet,
so sometimes you need wait for speech.