en_tn/jhn/01/15.md

He who comes after me

John is speaking about Jesus. The phrase "comes after me" means that John's ministry has already started and Jesus's ministry will start later.

is greater than I am

"is more important than I am" or "has more authority than I have"

for he was before me

Be careful not to translate this in a way that suggests that Jesus is more important because he is older than John in human years. Jesus is greater and more important than John because he is God the Son, who has always been alive.