In him was life, and the life was the light of men

"In him was life" is a metonym for causing everything to live. And, "light" here is a metaphor for "truth." AT: "He is the one who caused everything to live. And he revealed to people what is true about God" (See: rc://en/ta/man/translate/figs-metonymy and rc://en/ta/man/translate/figs-metaphor)

In him

Here use a general term for "life." If you must be more specific, translate as "spiritual life."