Why elections should be held in a democracy ?

The nature of democracy is that elected officials are accountable to the people, and they must return to the voters at prescribed intervals to seek their mandate to continue in office. For that reason most democratic constitutions provide that elections are held at fixed regular intervals.

answer; (you have the right of way);

an informal structure in a bureaucracy would be something like so-called "office politics". where there's a formal structure set up for the organization, but then an informal subculture as well that has a way of organizing the bureaucracy further. this can be positive because it sets up an added degree of organization, albeit informal, within the bureaucracy.