This phrase is used here to mark the beginning of a new part of the story. If your language has a way for doing this, you could consider using it here.
Translators could add a footnote saying: "It is not clear whether this refers to heavenly beings or human beings. In either case, they were beings that God created." Some believe these words refer to angels who rebelled against God, that is, evil spirits or demons. Others think this may refer to powerful political rulers, and others think this may refer to the descendants of Seth.
"They will live one hundred and twenty years." Possible meanings are 1) the normal lifespan of people would decrease to 120 years. AT: "They will not live more than 120 years" or 2) in 120 years everyone would die. AT: "They will live only 120 years" (See: [[rc://en/ta/man/translate/translate-numbers]])