@andreasMch In standalone mode you must query rr_reply as well if you need the G-code response. To know when a new response is available, you should monitor seqs from rr_model as documented in the documentation article.
I'm not super familiar with Orca slicer, but normally in if you leave out the temperature commands from your start gcode, the slicer will insert it's own using the temperature you've set in the settings.
@TypQxQ that's a long write time on the SD card. I would suggest refreshing the SD card (don't forget to back everything up) or replace the SD card for a newer one