Error when installing macOS Sierra via internet recovery mode

Recently I’ve erased, recovered and updated my Mac Pro from correctly installed Catalina to Ventura.

My old (2016) Mac wasn’t able to handle the new system and became too slow.

To downgrade the iOS I erased disks and run internet recovery.

ios sierra has been identified as a first compatible iOS, but installation preparation ends with an error.

3 sec before finishing the process the following message appears:

“About -398 seconds remaining”

And an error message additionally.

in my disk utility I see:

Apple SSD APP0256J media

• Macintosh HD (format: MacOS Extended (Journaled)

Apple disk image Media

• OS X Base System

first Aid shows that all is fine.

any idea what to do next?