While in game, Escape>Change Keys> in the right corner checkbox called “Double tap ‘jump’ to toggle fly”. For flying faster, you can press J (by default?) to enable fast mode, you can change how fast it is in the settings menu, in the main menu. This is all assuming that you have the ‘fly’ and ‘fast’ privileges.
All players should check the settings menu at least once, I changed many things in there, and you should too. One of them was enabling the crosshair in the Touchscreen menu on mobile , it enables a much smoother experience on mobile.
Thorned_Rose