Hello,,
in post from Roland was a hint to a further Barcode-App "Barcode Scanner + (Plus)"
This Barcode-App is a "for-pay-App" (1,09 €)
I installed this App on my device and started my GMA-App.
The the GMA-Frontcall asked to use the new App!!
So you can install the new App and have a Portrait Barcode-Scanner, without changing the GMA-App.
Thanks Roland.
https://play.google.com/store/apps/details?id=com.srowen.bs.android