Question

how Belgium government solve ethnic composition

Answer 1

by making community government

Answer 2

Dutch and French speaking ministers are equal in the central government.

Some of the Powers of the central government have been given to state governmentt. The state governments  are not subordinate to the central government.

Brussels has a separate government where both the communities have equal representation.

There is another government  called community government  elected by the people belonging to Dutch, French and German.