You have written a very long essay. I am not sure that you can deal with the 40 minutes.
I see some ideas are gone for the topic.
To solve this, it is always better to start analyzing the prompt before writing the essay:Fact:
People nowadays live longer than they used to.Task 1:
What caused this situation? (the first body)Task 2:
Is it a negative or positive development? (the second body)For intro:
A writer needs to keep in mind that the intro is often what a reader remembers best. Your intro should be the best part of your essay. If you could, state your own opinion in the introduction itself with a statement expressing your opinion very clearly.
To begin with potential merits, as we are stepping on this modern era of world which is driven by advanced form of technologies and lots of other advancement everybody has strong proclivity for living life with fullest use of these development. Thus, we are avoiding muscle demanding work but intensively using machinery aides.This is gone for the topic.