Question: how to restore whatsapp chat from db file?
Answer: Download a file manager app. In the file manager app, navigate to sdcard/WhatsApp/Databases. ...  Rename the backup file you want to restore from msgstore-YYYY-MM-DD.1.db.crypt12 to msgstore.db.crypt12. ...  Uninstall and reinstall WhatsApp. Tap RESTORE when prompted.