Thank you for taking the time to read my post and reply.
When I trade FOREX, I can Buy or Sell, at the Market, and then end the trade whenever I want.
For example, let's say I Buy at $10. It increases to $10.5, $11.0, etc. I can get out of the trade whenever I want to. I don't want to get out of the trade because I believe the price will keep going up and up.
Is this possible when I buy Bitcoin in Coinbase?
Yes, but do not use a market order for selling, it will lead you to sell directly even if the price is lower than the market price at the present time because it is an order for the purpose of providing liquidity and executing the order directly regardless of the price. Use the sell option with a price limit and wait for the order to be executed by waiting until The average price on the platform is equal to the price at which you sell.
I suggest that you start with a demo account so as not to lose your money. In that account, you can trade with zero virtual money for the purpose of learning.