but you told me to smoke one cigar a day almost killed me first.

Haha, your sentence comes from a joke. An old man went to see a doctor. The doctor thought that the old man was caused by smoking, so he asked him to reduce his smoking by two cigarettes and let him smoke one cigarette a day. But in fact, that The old man never smoked, but after a period of time he went to the hospital for a review. The doctor saw that the old man's condition not only did not improve, but worsened, so he asked the old man why, and the old man said this.

So the meaning of "first" here is: it was smoking that made my condition worse (killed me).

This first is also a punchline in the joke.

The translation is a free translation, not a literal translation. The literal translation should be: But you said you let me smoke one cigarette a day, which almost killed me.

No phrase.

Man, there are only a few words and phrases, but the grammar is a little bit good. The most basic syntax.