I Corinthians 3:9: Everyone who is saved is to labor together with God. We are to team up with God as we build up the Body. We are to do our part (Romans 10:9-14). God does His part (John 6:44).
I Corinthians 3:10: Paul is the Masterbuilder. He is the chief constructor who has God’s plans; and he directs the work. He did not create the plans himself (Galatians 1:11 and 12). He is the foreman (Romans 11:13).