Im new to trading, there are so many coins and I keep reading about bitcoin being unsustainable regarding energy it uses to mine and there are coins coming out with faster transactions time.
If this is the case, Why is bitcoin considered the main one and its price not crashing from the threat of these other more equipped coins? Is bitcoin still able to develop and evolve and become energy sustainable and compete with faster transaction times if it is decentralized? No one is able to improve it?
You can't just trust everything that you read, there's a ton of people in crypto who are interested in seeing their coin surge, even if it means spreading negative information against other coins.
Bitcoin is not unsustainable, mining rewards are decreasing with time, so the need for PoW is not infinite like some minsinformed or dishonest people say.
Transaction speed is a matter of security - many coins have block times of a few minutes or less, but their confirmation are not as secure as confirmations of Bitcoin. This is why when you deposit Bitcoin, you are required to way 1-3 confirmations, but with Ethereum it's 10-20 confirmations and more. The real game-changer of transaction speed is Bitcoin's Lightning Network, its transactions are nearly instant.
Bitcoin is the king of crypto because it's simply better - all other coins achieve lower fees or faster transactions by trading off their security and decentralization.