Don’t think Strava app will do turn by turn. If you had a Garmin that does turn by turn you can get the GPX for the route and turn it into a route for the Garmin. It takes a little bit of faffing to get onto a Garmin, and getting a GPX off Strava that isn’t your own ride requires a premium account or asking the person for the GPX file.
There are likely other apps for the phone that will do turn by turn. Don’t know much about iPhone apps though so can’t comment, except if you want something that you can pull out and check the route then ViewRanger is worth a look. Not sure but it might do live turn by turn.
Noting that off road turn-by-turn is tricky when trails are close together. GPS isn’t that accurate, though you soon find out when you’re down the wrong one.