There are no "official" websites for Bitcoin related resources. There are only sites that are more "trustworthy" than others.
You can buy bitcoins with a wide variety of methods, ranging from person to person trades to buying bitcoins on exchanges. These exchanges can be regulated centralized services or decentralized, unregulated services. Depending on your situation, you will have to pick a method that suit your preferred use case.
As a newbie, I would suggest that you go with the regulated exchanges as your first option and then experiment with the other methods much later.