The first Adam became a living being
Paul quotes Genesis 2:7 about Adam becoming a living being. He then calls Christ the last Adam and a life-giving spirit.
It is sown a natural body; it is raised a spiritual body. If there is a natural body, there is also a spiritual body. So it is written: βThe first man Adam became a living being;β the last Adam a life-giving spirit. The spiritual, however, was not first, but the natural, and then the spiritual.
Genesis 2:7 says that God breathed life into the man and he became a living being. First Corinthians 15:45 introduces those words with, "So it is written," before speaking of the last Adam.