You can try this https://www.advancedcustomfields.com/resources/querying-relationship-fields/
or you could try implementing this https://www.advancedcustomfields.com/resources/bidirectional-relationships/
or you could try out a plugin like https://wordpress.org/plugins/post-2-post-for-acf/
The last 2 will not update the relationships automatically. You’d need to edit all the posts on one side or the other. There are a lot of topics here on the forums about the first option, but I generally use the last one.
