Thanks to Google and other posts from Steem I've found in order to "Power Up" my account in order to withdraw my money !
Since I was not online, Steem put my account on Power Down mode:
The solution I found was simple and worked:
I had to deposit few SP (1.215 SP) to my account, using: https://blocktrades.us/
Few minutes later, when the transaction was confirmed, I was able to sell my Steem (Tradeable tokens that may be transferred anywhere at anytime.) for Bitcoins.
Thanks to 
Your solution works fine also with bitcoins or other cryptocurrencies, using https://blocktrades.us/
