You can do selling off your bitcoins by  different ways and  most popular way is, selling through the online exchanges.  You need to find any site where you can sell your bit coins and making a  sell order  order and after this need specifying the amount of bitcoins at  you want to sell them  now when  someone places a ‘buy’ order according to your needs then you can exchange and  amount is credited to your account in the desired currency.

Hello,
 
I have learned everything about bitcoin.
 
Now i want to know that mining machine.
 
Please recommend me any one machine which i choose
 
1) Antminer R4       2) Antminer S9
 
And i am looking for Antminer S9 which have 13 TH's. So i can make 0.28 BTC after reduce of electricity cost.
 
Waiting someones reply.