Casually: あなたたちはかっこいいよ (anata tachi wa kakkoii yo)
Politely: あなたさんたちはかっこいいです (anata san tachi wa kakkoii desu)
'Kakkoii desu.'
bishounen: a young good looking guybishoujo: a young good looking girl
鬼 /o ni/ is a good Japanese equivalent for what you are looking for.
You can say le-le or liyo.https://www.livinglanguage.com/community/discussion/315/saying-youre-welcome-in-japanese-not-recommended
かっこいい (kakkoii)
'Watashi no kawaii oi Chan to mei Chan tachi.'
watashi / boku WA sukottolandojin desu watashi if youre female boku or ore if your male
If your question is, "why would a girl say youre not old looking?", then they probably think you are cite like a little kid. I have that exact problem. Goodluck.
youre a great friend
looking good
you are looking good
Sayonara .
You may say 'oshare' in Japanese; it means "fashionable," "stylish."