If none of the native speakers want to answer: This seems to be just colloquial (male) Japanese, i.e. phonetic shifts and simplifications in a somewhat rough style. じゃ=では ねー=ない んだ=のだ そりゃ=それは だろ=だろう So you get 俺たちだけでは勝ち目ないのだ。それはわかるだろう？ Trying to imitate the style: We alone ain't got a chance, see? You got this, don't you?