They changed from having a buffet to having a set menu
セットメニュー - set menu
バイキング - buffet
変更 - change, switched
They changed from
They switched to
They changed from having a buffet, to have a set menu
They switched to a set menu from a buffet
It looks like the buffet has been changed to a set menu.
・It looks like the buffet has been changed to a set menu.
「バイキングがセットメニューに変更されているみたい」
It looks like...(〜みたい)を使うことで伝えられます。
・Apparently, the buffet was replaced with a set menu.
「どうやらバイキングがセットメニューに変更された(置き換わった)らしい」