err..more context?

Name: Chad
Scripture: Luke 21
Truly I say to you, this generation will not pass away until all has taken place. Heaven and earth will pass away, but my words will not pass away.

OAP: Anyone notice some slight problems with these sentences? For one how about, heaven and earth passing away, heaven = passing away = not eternal = uhoh? Or let's skip that for now and go back to the most obvious, the generation that Jesus is speaking to is now dead, they have been for some time. Without a doubt they have passed away , the clear question now to ask is what is supposed to have taken place. The coming of Jesus on a cloud with power and great glory....
AH HA! you say, I must have not read for context and am grossly mistaken. Nope, as far as I can tell there is a fairly clear context concerning the end of the world.

God, it has become extremely clear to me in the past few weeks that I don't understand much of your word. Console me here, teach me what I need to understand and make clear what I can use to advance your kingdom. I can't see any part of your word being unimportant but obviously there is some that is over my head and logic, let me trust in you and use these times to speak to me. I trust you.