in Korean language, the subject is often omitted, so if you want to say "i love you" 당신[dang sin, you]을[ul, postposition for object] 사랑[sa rang, love]해요[hae yo, do] 당신을 사랑해요 당신을 사랑 합니다[hab ni da, do but more polite] both works fine.

"Sa Rang He Yo" is mean that " I love you". "Nal Sa Rang Ha Ni ?" is mean that " Do you love me?" haha^^