"'Lord,' I replied, 'these men know that I went from one synagogue to another to imprison and beat those who believe in you. And when the blood of your martyr Stephen was shed, I stood there giving my approval and guarding the clothes of those who were killing him.'" NIV translation
Paul's answer to God was that he had been one of them and they knew it. To him, it did not make sense that they would not see the change in him and believe in Jesus. The same thing happens to many Christians today as people from their past (before they came to Christ) do not want to see the truth of what God has done and is doing in their lives. We can take comfort in the fact that this is nothing new as it even happened to Paul.
"'Then the Lord said to me, "Go; I will send you far away to the Gentiles."'" NIV translation
So, Paul received his ministry instructions directly from the Lord and they weren't what he expected. Remember that Paul was not just a Jew but one of the most educated (a rising star in the Jewish leadership) but now God is going to send him to the Gentiles (non-Jews).
We, like Paul, must just trust in God and know that His wisdom and ways are above our understanding. When He speaks, we act in faith just as Paul did.
"The crowd listened to Paul until he said this. Then they raised their voices and shouted, 'Rid the earth of him! He's not fit to live!'" NIV translation
The crowd was calm until Paul said something that they did not like. They did not accept the fact that Gentiles could be children of God with the Jews and so they wanted him dead. Paul had to have known what their reaction would be but he still shared what Jesus had told him and trusted in God. We, too, will face times when people do not like what God says through us and even more in the last days.
"As they were shouting and throwing off their cloaks and flinging dust into the air, the commander ordered Paul to be taken into the barracks. He directed that he be flogged and questioned in order to find out why the people were shouting at him like this." NIV translation
The mob was going crazy so the commander just assumed that Paul had done something wrong and ordered that he be beaten and questioned about the matter. This may sound strange but the same type of thing happens today in many parts of the world. When some people don't like you sharing God's Word, they get a mob to try to stop it. Sometimes, this leads to false accusation and even arrest and unjust punishment as in the case of Paul here.