Flowbacknomad Does it happen automatically?
No, everything is deleted on your phone when you flash GOS or stockOS from google.
You'll have to back up what you want to keep and confirm that your photos, contacts, music, podcasts, messages, etc are elsewhere not on the phone before you flash GOS.
Export signal messages, perhaps screenshot the home screens on your phone to see where you placed all of your app icons. Export your calendar if it isnt linked to a google account. (See if you can view you calendar on a PC to verify)