in the derelict apartment building how do I get past the Fallen stuff? And how do I [u][/u]get out?

if you see the box on the stairs jump on it then turn so you are facing the stairs going down to the previous floor. then back all the way up to the wall and do a jump (can't remember if it is running or not, i think it is) then while in mid air press action and you will catch a ledge and vuwala you are on the next floor. don't worry i had a huge problem with that part
hope this helps