I recommend that you go to Localbitcoins.com, there you can make your offer and wait until someone seems your price and decide to make the trade, what if I advise you is to look at the reputation of the person so you have more security . There is also another platform called Uphold, which is quite acceptable in terms of security, since it is managed from a third party, and until the money is received, the Bitcoins can not be released, and in case of canceling and not paying, the same platform is responsible for paying the debt.