According to Luke, Paul left where he was and went to the house of a man named Justus, who loved and worshipped God and lived right next to the synagogue. This shows that Justus was a helpful friend to Paul, providing him a place to stay near where people gathered to learn about God.
Acts 18:7: And he departed thence, and entered into a certain [man's] house, named Justus, [one] that worshipped God, whose house joined hard to the synagogue.
This verse focuses on the promise of salvation through belief in Jesus Christ, which does not directly contradict Acts 18:7 but contrasts with the emphasis on geographical change and companionship found in Acts 18:7.
Acts 16:31: And they said, Believe on the Lord Jesus Christ, and thou shalt be saved, and thy house.