How are the Belgium are changed …

Federalism is a system of government under which power is divided between a central authority and its various constituent units.
In federal government power is shared among the different levels of government but in unitary government all powers are in the hands of a single unit.
The Belgium leaders tried to solve the ethnic problem by respecting the feeling and interest if different committees and regions by establishing a federal government, where as the Sri Lankan Government tried to solve the problem through Majoritarianism.
Federal govt is far better than the unitary govt as the federal govt involves the concept of power sharing and that involve the active participation of people and effective decisions in favour of the people.

for eg in belgium who divided its govt powers into central, state and community govt, was a successful amendment with no conflicts.