Grammatically, I don't see any issue. If you say or text your introduction to any Korean speaker, every single one will definitely understand what you are saying. The improvements could be two things: conjunctions and nuances. You are listing sentences without conjunctions, so your introduction sounds like example sentences from a language textbook. If I were you, I would probably reorder sentences and combine them together with some conjunctions. For instance, 안녕하세요, 제 이름은 안나라고 하고요 열여섯 살이에요. 저는 오빠 한 명과 여동생이 있어요. 제 취미는 그림이고 학생이에요. 만나서 반가워요. The next thing would be nuances. The above my example is fine, but I highly doubt any Korean teenagers speak like that. The sentences give the nuances of 20s/30s introduction vives in formal places such as work offices or meetings. This is kind of the hardest part, but sadly this is what it is. Hence, if I re-write your introduction like a real Korean teenager girl, it would be something like 안녕하세요! 전 안나라고해요. 전, 제 위로 오빠한명 그리고 아래로 여동생 한명있는 열여섯살 고등학생이고요. 취미로는 그림을 그려요! 만나서 반가워요! Hopefully, it helps you. Good luck!