First, I would like to recommend YouTube for this type of question which will guide you more through a demo. I am answering 1 and 3 questions. There are many plate forums, websites, and exchanges that will help you to trade, buy, or sell and another one is the P2P method in which you can buy or sell a cryptocurrency directly from the users. The third question answer is that there are many reasons why Bitcoin is better than conventional currency.
> More secure and anonymous form of payment.
> Globally form of payment
> More scarce form of currency.

For the 2 questions check the replies of some legendary members they will understand you in detail.