Replaced S9 screen and now boots in TWRP

/e/OS Devices Samsung
1

Happily installed /e/ on Smasung with easy installer, as I have zero technical knowledge. After replacing my broken screen, the phone turned on with a TWRP partition &/ read only message (cannot recall exactly) but the shop tech swiped to allow ‘modification’, I think. Now thrying to research i realise i have no clue. Why is this happening? If there is a way to get back to /e/ please advise, or if I need to restore, how would i go about backing up my data, and then would I need to reinstall with the easy installer?
Thanks!

Regain your privacy! Adopt /e/ the unGoogled mobile OS and online servicesphone

2

Did you already try this from TWRP

Reboot > Reboot system

Reboot is on the main menu of TWRP, if you do not see it press the Back button, till you get to this main menu.

3

It seems strange, but I can recall a situation like this and it turned out one of the connectors was not put in place during screen replacement procedure.
But this was on a model before your S9, but maybe keep it in mind — after all it has been taken apart entirely.