For A Sign

Luke 11:29 ESV
29 When the crowds were increasing, he began to say, This generation is an evil generation. It seeks for a sign, but no sign will be given to it except the sign of Jonah.

Does it make sense or is it logical to accept the resurrection of Christ by the Holy Spirit, but deny that same power of God in his birth?
Is this compatible with belief in a risen Son of the living God, confirmed by many miracles and signs?
Are there some parts of gospel which are too hard to believe? Our acceptance or denial of God has no bearing on the truth of God.
Jesus said one sign would be given to unbelievers, the sign of Jonah.
What would be the sign for believers?