Hello :) -ㄴ 것 같아 means that you think you did something in the past. For example: 그는 벌써 학교에 간 것 같아요. = I think he already went to school. Hope you'll get what i mean :))

It's got a whole other different meanings but basically '것 같아요' can be said when the speaker is not sure about some fact or how he/she feels. something like "I think..." "It might..." "It's probably..." "I'm guessing..." "I remember that..." examples: 부장님이 그 일을 이미 다 한 것 같아요 (It seems that the boss already did all that work.) 옆집에서 사는 사람은 그 소나무를 자른 것 같아요 (It seems that the person who lives in the house next door cut that pine tree.) 저 사람들이 그냥 가? (Are those people just leaving?) 응… 가는 것 같아 (Yes, they are probably leaving.) Source: https://www.howtostudykorean.com/unit-2-lower-intermediate-korean-grammar/unit-2-lessons-34-41/lesson-35/