Start with something that is already happening.
Ask whether they have done the route before, how their journey was, what they think of the place or whether they know many people there. Those questions are easier to answer because they do not ask a stranger to produce an interesting life story on command.
A shared activity also gives both people permission to look away, walk, play or pause rather than maintaining intense eye contact through every second of the conversation.
Follow one answer instead of firing the next question immediately.
If somebody says they came from Manchester, you can respond to that, mention your own journey or ask what made them choose this event. That feels more like a conversation than moving through a checklist of job, relationship, hobbies and hometown.
You do not need to collect enough facts to decide whether this person could become a friend before the event ends.
Share enough of yourself that they do not have to carry everything.
Questions are useful, but a string of questions can make somebody feel examined. Add your own small answer, opinion or experience so the interaction has somewhere to move.
That still does not require instant oversharing. Friendship can build from ordinary information first and become more personal when trust exists.
End conversations normally instead of forcing them to last.
At a group event it is completely normal for conversations to stop, split or restart later. You can go for a drink, rejoin the activity or talk to somebody else without announcing that the interaction has been judged unsuccessful.
Repeated smaller conversations across a day or across several events often create more familiarity than one intense forty-minute chat.