Can we not have this conversation with the assumption that I would live until I am 80 years old?
Because I think I will die much earlier than that.
ご質問ありがとうございます。
"Can we not have this conversation"＝「この会話はしないでくれますか」
"with the assumption that I would live until I am 80 years old?"＝「私が80歳まで生きるという前提で？」
"Because I think I will die much earlier than that."＝「なぜかというと、私はそれよりももっと早く死ぬと思うので。」
ご参考に。
アメリカ合衆国 
