There are plenty of ways to buy Bitcoin. It depends on the country where you are from other options. Do you want to buy it for real money (I mean dollars, euro)?
Stay away from intermediaries and other people who suggest you selling BTC. They can deceive you and leave empty-handed. So stay away from such suggestions.
Also, before buying Bitcoin you should research the market situation and its behavior in order to buy for a good price and avoid possible huge losses.
The best cryptocurrency exchanges today are: Binance - https://www.binance.com/
                                                                Bittrex - https://bittrex.com/
                                                                Huobi - https://www.huobi.com/.
But they do not accept fiat money at the moment.
The one exchange I personally know is good for buying BTC for money (because I used it myself) is CEX (https://cex.io/). There you can buy Bitcoin safely via your credit/debit card.