1: [D.1.a]Then what advantage has the Jew? [1 - numbering the questions in the sequence] Or what is the value of circumcision?[1a]
These two questions are in parallel to each other. To be a Jew is to be circumcised. To be circumcised is to be a Jew. The rite is for men only, a symbolic death. The issue of advantage is a point of inner conflict for Paul - these questions are his inner struggle. Yes, he is an apostle, but even he does not realize the extent of his message - the questions are his self reaching for explanation. In holding to the unity he desires, he will extend unity to many more groups than he imagines.
2: Much in every way. To begin with, the Jews are entrusted with the oracles of God.
3: What if some were unfaithful? Does their faithlessness nullify the faithfulness of God? 
4: By no means!
Let God be true though every human be false, as it is written, "That thou mayest be justified in thy words, and prevail when thou art judged."
5: But if our wickedness serves to show the justice of God, what shall we say? That God is unjust to inflict wrath on us? (I speak in a human way.)
There are many silly questions about God - and we might well doubt God, given the violence of the human condition. God's faithfulness is not compromised by doubt or violence.
6: By no means!
We may continue in sin if we must, but what is the sin we continue in? Is it our own need for confessional correctness? or for beauty of tradition? or for the moral life? All of these are 'of the flesh' (our fragile human condition) on their own. Only with the Spirit enlivening the flesh of the body is life possible. So Paul can put the question here - not for ridicule, but as part of his 'self-evident' reasoning about God through his knowledge of Christ Jesus in the Spirit. The issues that are self-evident, he dismisses with the 10 refrains (3 here, 4 in chapter 6-7, and 3 in chapters 9-10 - I think these groupings are significant of Paul's mind - a kind of 1-2-3 (subdivided) of his reasoning.)
For then how could God judge the world?[3a] 7: But if through my falsehood God's truthfulness abounds to his glory, why am I still being condemned as a sinner?[3b] 8: And why not do evil that good may come?[3c] -- as some people slanderously charge us with saying. Their condemnation is just.
End of the first half of the advantage of the Jew - subject will be returned to along with the remnant theology in chapter 9.
9:[D.1.b] What then? Do we excel?[4 - a one word sentence but one of the major questions - related ultimately to the last questions on the justice of God towards
Heavens, no! - the issue of all being under sin is not confession, tradition, or morals - none of these 'holy' laws. The issue of sin is inscrutable; it is only revealed by the presence of the Spirit enlivening the body - then one says - aha - depart from me Lord for I am a sinful person. And the Lord says - no way - you and I have work to do, a love to live, a good will to prove. Note the massive usage of the word sin in this section of the epistle (especially 5-8.10), 3 times more here than in all the rest of Paul's writing combined (Dunn, Theology of Paul the Apostle).
No, not at all; for I have already charged that all humans, both Jews and Greeks, are under the power of sin, 10: as it is written:
"None is righteous, no, not one;
11: no one understands, no one seeks for God.
12: All have turned aside, together they have gone wrong;
no one does good, not even one."
13: "Their throat is an open grave,
they use their tongues to deceive."
"The venom of asps is under their lips."
14: "Their mouth is full of curses and bitterness."
15: "Their feet are swift to shed blood,
16: in their paths are ruin and misery,
17: and the way of peace they do not know."
18: "There is no fear of God before their eyes."
19: Now we know that whatever the law [including Psalms and Prophets] says it speaks to those who are under the law, so that every mouth may be stopped, and the whole world may be held accountable to God.
20: For no human being will be justified in his sight by works of the law,
since through the law comes knowledge of sin.
21: But now the righteousness of God has been manifested apart from law,
although the law and the prophets bear witness to it,
22: the righteousness of God through faith in Jesus Christ for all who believe.
For there is no distinction;
23: since all have sinned and fall short of the glory of God,
24: they are justified by his grace as a gift,
through the redemption which is in Christ Jesus,
25: whom God put forward as a mercy seat by his blood, to be received by faith.
This was to show God's righteousness,
because in his divine forbearance he had passed over former sins;
26: it was to prove at the present time that he himself is righteous
and that he justifies him who has faith in Jesus.
27:Then what becomes of our claim to honour? It is excluded.
On what principle? On the principle of works?[6a] No, but on the principle of faith.
28: For we hold that a human is justified by faith apart from works of law.
29: Or is God the God of Jews only? Is he not the God of Gentiles also?[7a]
Yes, of Gentiles also,
30: If indeed, God;
who will justify the circumcised on the ground of faith, is one
he will also justify the uncircumcised through that same faith.
31: Do we then overthrow the law by this faith? By no means! On the contrary, we uphold the law.
This series on Romans begins here