it is different whether there is "?" or not. if there is "?", it mean "날 찾았니?" if there is no "?", it mean "날 찾아" "you're going to find me, right?" mean "넌 날 찾을거야, 그렇지? " "I'm going to hold the cheering towel at the concert" mean "난 그 공연장에서 응원수건을 들고 있을 거야." and i think u try to write "날 찾을거지?" transfering to English, it is "will you look for me?" or "you will find me, right?" i'm sorry, not to have good detail for explanation.