He gave me the same warning/advice he had been given, but only because he clearly had not understood the essence or the context of the warning/advice.
The fact he gave me the same warning he had been given clearly shows he didn't understand the meaning in the first place.
Mさんこんにちは。
「注意」は英訳がいろいろありますが、'caution' 又は 'warning' を使うと「戒め」のニュアンスがします。'advice' を使うと「助言」のニュアンスが入ります。適切な言葉を選んでください。どちらも意味の少し広い範囲がありますが、意味が文脈で伝わります。
He gave me the same warning/advice he had been given = 彼が自分がされた注意を私にもした
本質 = essence
context = 状況・文脈
clearly = 明らかに
but only because he clearly had not understood the essence or the context of the warning/advice = それは彼が明らかにその注意の本質と状況を理解できなかったからだけです。
The fact he gave me the same warning he had been given = 彼が私に同じ注意をした事実は
clearly shows he didn't understand the meaning in the first place. そもそもその注意の意味を理解していなかったというのを明らかに表しています。
in the first place = そもそも
ご参考になれば幸いです。