Christians benefit from a closer look at the Biblical Fall Feasts, because, among other things, they foreshadow Christ's work in days to come. We have hindsight to help us see how Christ fulfilled Passover, Unleavened Bread, First Fruits, and Pentecost. We need foresight to see how he will fulfil Trumpets, Atonement, and Shelters.
This helps us understand why there are two New Years in the Jewish calendar: the religious-year cycle of teaching starts with Trumpets, but the calendar-year starts just before Passover. Some people start their spiritual lives at the beginning with Creation and the Old Testament, but some start with Jesus the Passover lamb.
The religious cycle begins with Trumpets for the beginnings of eras: Creation; a ram for Isaac; the Law of Moses. Atonement is made, and at Shelters we thank God for his presence. Then at Passover, Unleavened Bread & First Fruits we recall the Exodus. Pentecost calls for the second harvest.
And thus people lived... until the new cycle.
A new era of the Messiah is Trumpeted (think of the Prophets), the Saviour who will make Atonement, will Shelter with us - and scriptural clues suggest Jesus' birth around the time of Shelters - God-with-us in the flesh. At Passover/Unleavened Bread he makes the necessary sacrifice, then becomes the First Fruits of the resurrection, and at Pentecost gives his Spirit for the second harvest of Gentiles.
And thus people live… until the new era!
The final era will be Trumpeted at Christ's return, his prior sacrifice will be what Atones for us (covers us) on the Day of Judgement, and we will Shelter with him in Heaven.
And thus people will live… forever.
Whether you start with the Old Testament beginnings, or start with Christ's Passover, the feasts commemorate the whole history from beginning to end.