Being an expert in something means that you are good at it.
For example, I am not very good at football because I don't play it often and so I'm not an expert. But if you play football every day then you would be an expert at the game.
The same goes for Minecraft. People often ask me how to become an expert at Minecraft. I say that you can get there by only playing the game! You don't need any more tips than that. Moreover, check this website : https://speedwallop.com/minecraft-tools/ for amazing Minecraft tools which will take your game at top of the sky.