I want to invest money in Gold.
Where can I buy Gold and sell it later when the gold prices are high? (high in the market as shown in market NASDAQ/NYSE)
There are gold index funds. I'm not sure what you mean by "real gold". If you mean you want to buy physical gold, you don't need to. The gold index funds will track the price of gold and will keep you from filling your basement up with gold bars.
Gold index funds will buy gold and then issue shares for the gold they hold. You can then buy and sell these just like you would buy and sell any share. GLD and IAU are the ticker symbols of some of these funds.
I think it is also worth pointing out that historically gold has a been a poor investment.