They went into the ark: They refers to all the living species listed in verse 14. Went into the ark with Noah is repeated from Gen 7.9. Two and two can more naturally be translated “a pair” or “a male and a female.”

Of all flesh: flesh, as in 6.19, refers to living beings or creatures. In which there was the breath of life is the same as in 1.30. See there for discussion. Verse 15 may be rendered, for example, “One male and one female of every kind of living being went into the boat with Noah.” Bible en français courant translates “Pairs of every living species went into the boat along with Noah.”

Quoted with permission from Reyburn, William D. and Fry, Euan McG. A Handbook on Genesis. (UBS Helps for Translators). New York: UBS, 1997. For this and other handbooks for translators see here .