Please explain the following from Miller's Death of a Salesman:"You can't eat the orange and throw the peel away. A man is not a piece of fruit."...

I'll take a couple:

"you
can't eat the orange and throw the peel away. A man is not a piece of
fruit.-WILLY"

This is one of the most telling quotes in the
play.  Willy lives in the past, where relationships meant something in the workplace. 
In the modern "people eat people" (I never understood why dogs get blammed for our
behaviors) world, you can take the best from someone (the fruit), and throw away what
remains when it is no longer of any use to you.  Willy wants another world, in fact he
"lives" in that other world.

"after all the highways, and
the trains,and the years, you end upworth more dead than
alive."-WILLY

Willy wants to leave something for his sons;
he thinks they'll be able to get ahead if they have some "seed" money, so he comes to
think that if they can collect on his insurance policy after he kills himself, he will
be "worth" more to them than he is alive.  This is a sad commentary for two reasons.  No
one is worth more dead than alive, and they probably won't be able to collect on the
insurance policy anyway since insurance policies usually don't cover suicides (thus the
reason for the comments on some of Willie's earlier
"accidents.")

"he had the wrong dreams. All, all
wrong."-BIFF

This could be.  Willy was never a great
salesman; he just managed to scratch out a living.  We know that Willy was great with
his hands and that he enjoyed building things and growing things.  Might he have been
happier working in these fields?  Who knows.  If we knew at the end of our lives what we
know earlier, all decisions would be easier.

Good luck with the rest of your
questions.