Bitcoin has a lot of diverse options and methods in which it can be purchased or sold.
There are different payment methods for you to buy your first bitcoin: bank transfer, credit/ debit/ gift cards, etc.
After you have your bitcoin, you can have different trade types: Spot, Margin/ Leverage, Future, Binary/ Option tradings. You only sell your real bitcoin when you do it in Spot trading. For other types, what you sell is not your real bitcoin and it is just the credited amount to your account. You sell the credited amount, not real bitcoin because your real bitcoin will be move and lock in the cross or isolated account.
Different online companies stands as middle men so as their rates differs. Upstanding a company rules and regulations is a major tool for a successful transaction with bitcoin. Most of these companies which serves as middle men in the bitcoin transactions charges with respect to the time of delivery. Delivery time can be subjected to hours, days or even months as the charges lowers with longer time frame to be delivered. It is important to know and study carefully the particular option to choose when transacting with an online company so as not spend excessively your bitcoins without your proper knowledge.
Exchanges have taker, maker, deposit, withdrawal, conversion fees.
https://www.cryptowisser.com/exchanges/https://exchangewar.info/If you move your bitcoin to internal wallet on one platform, they can give free movements (a few times in a month). It is one of ways to save fees.