Can you pls tell me an official site
also can i buy and sell BTC or when i purchase i will keep it in wallet
What you Think about coinbase Guys other scam
I've suggested it above, it's legit. To make things easier and not get lost, use
BuyBitcoinWorldwide. Select the country you're from and the payment method you want to use and it will give you a list of exchanges you could use (reputable ones).