In order to open a new Buy or Sell position, it is necessary to have funds in your available balance.
CFD trading is based on strategy and sentiment:

• An investor who believes that the price of an instrument will rise in value will open a BUY position.
• An investor who believes that the price of an instrument will fall in value will open a SELL position.

By closing the position, the invested funds plus/minus any profits/losses made on the investment will be returned to your account balance.
It is important to note that each BUY or SELL position is a separate transaction.
In other words, opening a SELL position on an instrument you are already trading will not close your BUY position.
Each position is a unique investment.