How do I back up my data?

Go to Settings → Cloud Backup, pick one of iCloud, Google Drive, or Dropbox, and authorize it. After that you can trigger a backup manually anytime.

Backups go into your own cloud account, keeping the 5 most recent snapshots. Product photos sync incrementally — only new or changed images are uploaded. If the cloud and local versions ever diverge, DingPOS asks you which to keep — it never overwrites silently.