I say as little as possible whenever I talk to him.
I only say what I have to when I talk to him.
ーI say as little as possible whenever I talk to him.
「彼と話すときは最小限のことしか言わない」
to say as little as possible で「最小限のことだけ言う」
ーI only say what I have to when I talk to him.
「彼と話すときは必要なことしか言わない」
to only say what I have to で「必要なことだけを言う」
ご参考まで!
・I only talk to him about the bare minimum.
「彼とは必要最小限のことだけを話します。」
・We only communicate about what's absolutely necessary.
「私たちは絶対に必要なことだけを話します。」
ここで、"bare minimum" は「最小限度」の意味です。また、"absolutely necessary" というフレーズで「絶対に必要なこと」への言及を強調します。