24:22: "And except those days should be shortened, there should no flesh be saved: but for the elect's sake those days shall be shortened."
What Jesus is saying is that this is an exception. The 'elect' are all those who are believers in Christ, and we are included in that. What He means by saying that 'those days shall be shortened' is that all people will suffer these foretold judgements, except believers. This is one of the many references to what is called the 'Rapture', when we, and all believers, will be taken in an instant to be with Him in Heaven, meaning we will miss a great deal of the judgements.
24:29-30:"Immediately after the tribulation of those days shall the sun be darkened, and the moon shall not give her light, and the stars shall fall from heaven, and the powers of Heaven shall be shaken: And then shall appear the sign of the Son of Man in Heaven: and then shall all the tribes of the Earth mourn, and they shall see the Son of Man coming in the clouds of Heaven with power and great glory."
These event occur long after the rapture and right after the 'tribulation', the period of judgements. What Jesus is referencing now is the 'second coming', when He returns to Earth to judge all mankind.
Matthew 24:31: "And He shall send His angels with a great sound of a trumpet, and they shall gather together His elect from the four winds, from one end of Heaven to the other."
He will send His angels to gather all those who believe in Him, those who came to Him both before and after the rapture.
Matthew 24:32-33: "Now learn a parable of the fig tree; When his branch is yet tender, and puts forth leaves, you know that summer is near: So likewise you, when you shall see all these things, know that it is near, even at the doors.
This is a parable, or example. Jesus is saying that, just as you know by the leaves on a tree that summer is here, you will know when all of these foretold signs happen, that He is near.
Matthew 24:34: "Verily I say to you, This generation shall not pass, till all these things be fulfilled."
This is one of the most misunderstood verses in the Bible. Many people say that Jesus was talking about the generation of people He was talking to, but He was referencing the generation of people that see these judgements and signs fulfilled. That might be us, and it might not, nobody but God knows.
Matthew 24:35: "Heaven and Earth shall pass away, but My words shall not pass away."
No matter what happens, the words of Jesus Christ will never pass away.