(너) 미쳤어요? are you crazy? the 너 part is optional, it can be eliminated
당신은 미쳤어! you are crazy
보고 싶어요I miss you ( when you haven't seen somebody in while) or 그리워요 ( when you are separated by a long distance.
나는 너에게 관심이 있어 this means i care about you or interested. If you want to say I like you then you would say 나는 너를 좋아해
나는 항상 널 위해 여기 있을 거야 mean's I will always be here for you