V-기로 했어요
This pattern means "decided to do something." Form it with a verb stem + 기로 했어요. It is very useful for simple decisions in daily life. Example: "저는 섬에서 기다리기로 했어요." = "I decided to wait on the island." You can reuse it in sentences like "내일은 일찍 가기로 했어요." = "I decided to go early tomorrow."
저는 섬에서 기다리기로 했어요.
I decided to wait on the island.
