QR Translate App does use a local database inside a phone to save information, you can delete for example translation history or delete the App.
Language files which can translate to other languages are downloaded to a device coming from ML Kit from Google and can be used without internet enabled after download. If Google keeps any privacy information associated to those downloads or regarding ML Kit use, please take a look at Google's Terms: https://policies.google.com/privacy.
Besides acceptance of agreements (answers stored locally on a device), languages users want to translate to and App settings QR Translate App does not ask you to login to Google or another service.
QR Translate does not keep personal information from your app use stored outside of a device, but certain translation results temporarily, maybe about 1 hour remains a translation rest in memory, such translation result links stay in memory to be able to make shorter links and make QR codes smaller, if a translation is sent to a URL shortener QR Translate let you decide to send a translation request or not. No link between you and a translation result is stored by Qr Translate unless you write personal identifiable information in such translation requests
Privacy information might change later, but then people should be made aware of such changes.