"했는데 and 했어는데" => "했는데 and 했었는데" Both 했는데 and 했었는데 (not 했어는데 which is wrong) are correct and common. They are from the base form 했다 and 했었다 with the -는데 conjugation. - 했다: past form of 하다 (do, act, perform). - 했었다: past perfect(대과거) form of 하다. Indicates events further in the past. - ~는데: a connective form to express a background, reason, or contrasting situation to what follows. Example: - 내 친구는 강릉으로 이사했다: My friend moved to Gangneung.(simple past) - 나는 강릉에 살았을 때 바닷가에 자주 갔었다: I had gone to the beach often when I lived in Gangneung. (갔었다 indicates a past action relative to a past time point) - 준비 많이 했는데요: I have done a thorough preparation. (so I'm ready now) - 준비 많이 했었는데요: I had done a thorough preparation. (but that was in the past and may not be relevant now)