RuleUrInvoice - An Android shop billing app, looking for workflow feedback

I'm building RuleUrInvoice under FunMakerz, an Android billing and stock app for small shops. The idea is to keep the everyday jobs together: making a bill, finding products, keeping customer records and exporting backups. Local billing is designed to work offline, with optional online tools being tested separately. I'm working on a clearer UI now, but I don't want to confuse a nice screen with something ready for a shop counter. The latest redesign still needs APK and phone checks. Physical printing, camera behaviour and offline reconnect also need more real-device testing. There isn't a public APK download on the site yet. I'd like feedback on the workflow rather than a feature wishlist: if you run a shop or help at one, which task wastes the most time? And what would you need to see before trusting a phone app with your billing records? The site has app previews using made-up demo data and notes on what's still being tested: ruleurinvoice.funmakerz.online No customer records or bills needed for feedback. A description of the problem is enough.