Hi Adrian
P.S. very likely the cause of boot problems is on my side, not installer one. If I checked partitions with OSX and then with linux, it differs. And the difference is in my two grub partitions. Using disk tools from different OS causes some mismatch. I will reorganize disks, and for Debian will be dedicated one.Those aren’t boot-related issues, but you’re just missing the firmware for your graphics card. Please boot the machine with “nomodeset” and install the “firmware-graphics-amd” package.
Thanks for advice, I will do this first.
Adrian
Martina