发布到Firebase时，单元格会重复多次

I'm making an app in which I can post messages. I store my data in Firebase. When I'm posting a new message, that particular cell is duplicating multiple times (so I see the post like 2, 3, 4 or more times). But it's just one post in Firebase. And when I'm refreshing my screen (by for example sorting the data), it's just one post again. What am I doing wrong?I'm making an app in which I can post messages.