original: FIFA's supreme body is the FIFA Congress, an assembly made up of representatives from each affiliated member association.
simplifications: FIFA's supreme body is the FIFA Congress.  It is a group made up of representatives from each affiliated member association. FIFA's top body is the FIFA Congress. It is made up of people from every connected to it association. FIFA congress is assembled with reps from each affiliated member association. FIFA's supreme body is the FIFA Congress. It is an assembly made up of representatives from each affiliated member association. FIFA's highest ranking body is the FIFA Congress. It is an assembly of representatives from each affiliated member association. FIFA's supreme body is the FIFA Congress. It is an assembly made of representatives from each related member association. The FIFA Congress is made up of representatives from each member association. FIFA's supreme body is the FIFA Congress. The FIFA Congress is an assembly made up of representatives from each affiliated member association. FIFA's main group is the FIFA Congress, an council made up of reps from each  member of FIFA. FIFA's highest body is the FIFA Congress, a gathering made up of representatives from each affiliated member association.