Use APKPure App
Get Backup apk to SD old version APK for Android
Backup Apk auf die SD-Karte oder im internen SD**** Plz ermöglichen die Lagerung Erlaubnis ****
4 key feature
-app backup to sd
-install from sd
-uninstall from device
-share you app through facebook or whatsapp
**Don't forget to allow storage permission before user