WP probably works a lot different that what you are used to. In your example, suppliers, rooms and facilities should probably all be Custom Post Types. You should take a look at this https://codex.wordpress.org/Post_Types.
ACF is for managing custom data on posts and in other locations and not really for creating complex “things” or “objects”. In WP you can have multiple post types and then relate the posts to each other in the manner you are looking for.
ACF is basically a tool that does what anyone can do with custom fields in WP, it is just designed to make that job easier to that we don’t need to create all the admin forms ourselves, which is that hardest part of the job in WP.
