You can download your chat records via email by clicking the arrow icon on the top right part of your chat screen > Settings > Export Messages.
1. You can only receive the text messages that remain in your chat room (stickers, photos, voice memos, and GIF selfies not included).
2. Please make sure you received the backup email.
3. The backup mail is valid for up to 14 days once it's sent. Please download your chat record file within those 14 days.
4. If the download period has expired, you have to attempt the backup process all over again.