Mark's gospel answers two questions: who can give us access to God, and how will the do it?
(Who is Jesus, and why he must die)
Jesus clears the temple of money lenders and quotes Jeremiah 7 : "house of prayer for all nations, but you have made it a den of robbers"
Both God and people are being robbed when they are denied access to God.
Jesus curses the fig tree and it withers, indicating access to God will no longer be via a fruitless temple.
Peter knows Jesus is the Christ, but does not yet understand why the Christ has to die. Like the blind man healed in two stages, he sees but not clearly.
To be a follower of Christ is to deny yourself and take up your cross.