저는 당신을 위해 과자를 만들었어요. 맛있게 드세요! I made these cookies for you! Please enjoy! 감사합니다 :)

This is already good, although we would keep the second half of the sentence in the present tense. So we would say "I made these cookies for you, I hope you like them (or I hope you enjoy them)." I hope that helps :)

난 너를 위해 이 쿠키를 만들었어. 맜있게 먹어. :)