Yes, you can sell stocks before buying them in trading. 

For example, let’s assume a stock is trading at ₹200. If you expect the stock price to go down during that trading session, you will profit by selling them first and later buying them when the stock price goes down. If you sell the first at ₹200 and then buy them at ₹180, you will make a profit of ₹20. However, if the stock prices go against your expectations, you will make a loss.