If you mean the Spanish ''por'' as in the English ''for'', its για (gia).
The question "Por que la pregunta mean in English" translates to "Why does the question mean in English?" in English.
For your
if
es por ti = is for you
por auto = by car
por kay (spelt 'por que') is simply "why"; e.g. 'por que no?', "why not?"
"Por su puesto" translates to "of course" in English.
por la vida= for life
Finally
of course
why not