The first two instances of the word "you" are plural and refer to the Jews to whom Paul is speaking.
Here the words "we" and "us" refers to Paul and Barnabas but not the crowd that was present. (See: [[rc://en/ta/man/translate/figs-exclusive]])
Paul's quotation is from the prophet Isaiah in the Old Testament. In the original passage, the word "I" refers to God and the word "you" is singular and refers to the Messiah. Here, Paul and Barnabas seem to be saying that the quotation also refers to their ministry.
This can be stated in active form. "Word of God" here is a synecdoche for "message from God." Alternate translation: "that we speak the message from God to you first" or "that we speak the word of God to you first" (See: [[rc://en/ta/man/translate/figs-activepassive]] and [[rc://en/ta/man/translate/figs-synecdoche]])
Their rejection of the word of God is spoken of as if it were something they pushed away. Alternate translation: "Since you reject the word of God" (See: [[rc://en/ta/man/translate/figs-metaphor]])
"we will go to the Gentiles." Paul and Barnadas were implying that they would preach to the Gentiles. Alternate translation: "we will leave you and start preaching to the Gentiles" (See: [[rc://en/ta/man/translate/figs-explicit]])