From Shanghai:
the last train is at 1745;
the last bus to Tunxi Bus station is at 1712;
the last bus to the scenic area is at 1840;

From Hangzhou:
no direct train to Huangshan;
the last bus to tunxi is at 1630;
the last bus to scenic area is at 1510.
Just for reference, I got them from inernet.

And from where in Shanghai are starting the last buses to Tunxi or Scenic Area ? How bo book them, I need a ticket on 8 of october and arrive only in the morning ?

Shanghai South Bus Station. You can call to book the ticket, I am not sure if there is English service. You are arriving that day morning right? You may go there directly and buy the ticket for last bus. The Golden Week is over and the bus ticket is not hard to buy then. Good luck to you.