I don't know how, but I made my navigation disappear. (I don't know what's the real name of it)
What I'm missing is this:
Anyone has an idea how to get it back? :x
There is an easy way to re-enable the navigation gizmos via the Viewport interface. Simply toggle the button in the top right (or bottom right, if you've flipped the header to bottom) of the 3D viewport for 3D gizmos.