matame ahora means kill me now
It means, "and now that" or, if it is phrased as ¿y ahora qué? it would mean "and now what?"
Ahora es means "Now is'
ahora mismo = right now. Donde estas ahora mismo = where are you right now.
but now
"Que vas a hacer ahora?" means "What are you going to do/make now?"
"Where are we right now?"
take me now
Translation: Not today my love
It means "You do now"
I cannot speak now
now or never
That means "saying now".