In context of this topic, I find your name very fitting. hahaha, I love it!
Regarding Acts 9:22, Paul’s proving Jesus is Messiah to the Jews is actually not as abstract as our contemporary time. First, the Jews already believed in God. Secondly, the Jews already have the OT, which Paul uses to prove Jesus as the prophesied Messiah (see also his repeat MO in Acts 17:2-3), just as Jesus did on the road to Emmaus in Luke 24:25-27.
Today, since we are not conversing with Jews, we have to prove/defend (apologia) Christianity with God’s existence and then Jesus as the Messiah.
God’s existence is actually not as hard to prove scientifically and philosophically as we all think. We can always use, but not limited to, the 6 major points.
3 of them are scientific: Origin of the Universe, Origin of Species/Human/Living Creatures, and the Fine-tuning of the Universe. The non-theists have no answer for these 3 aspects.
Then we can also argue from the other 3 philosophical points (Objective) Morality, Free Will, and the Human Mind (Consciousness and Reasoning), to which the non-theists are cornered to believe that free will is an illusion that we are pre-determined by chemical reactions, formulating our reasoning, choices, and arbitrating our own morality.
Lastly, proving Jesus is actually not hard, because His existence and deeds are historically and archaeologically verifiable. And all scholars, even non-Christians, who looked into the evidence will not deny. (See Bart Ehrman)
Proving His divinity though is also not hard, as we just have to look at the prophecies He fulfilled, and even Jesus’ prediction of His own resurrection, which are all empirically verifiable. Lastly, we can tie it all up with how the OT has always pointed to this Son of God, Son of Man, Son of David, and all other titles Jesus claimed of His Godhood and Messiahship (He proved it with the 4 Messianic Miracles: Healing a man born blind, casting out a mute evil spirit, healing lepers, and resurrecting Lazarus after 4 days. Read about it, and you will see its significance in the Jewish context of Jesus days.)
I’m sorry I don’t go into details and only barely scratching the surface, as I try to be as brisk as possible. But I hope it helps and encourages us in our Christian faith.