The walkthrough to follow.
On javascript you should
– get the user ID (there are functions to do that)
– add it to the ACF ajax query.
For the other fields depending on user ID value :
On PHP you should use query filters (there are some for taxs, posts, relations)
– get the $_POST[ID] (added by JS before)
– use it.
When you load the page (ie for an update) , $_POST[ID] does not exist but you can use get_field if you need to use your query filters with user ID
