Solution Steps

1. Settings → General → iPhone Storage → Review storage breakdown.
2. Delete unused apps: Tap app → Delete App.
3. Offload unused apps: Settings → App Store → Offload Unused Apps (keeps data).
4. Clear Safari cache: Settings → Safari → Clear History and Website Data.
5. Delete old messages: Settings → Messages → Keep Messages → Change to 30 days or 1 year.
6. Delete photos/videos: Photos → Select → Delete (or use Recently Deleted).
7. Update iOS: Settings → General → Software Update (can free up space).