Editing of individual items and saving them

I am working on an application where I have to ask customers for input. Categories are on the left side of the page. Inside one category user needs to fill the details of multiple items. User will be prompted with items 1, he fills the details, he can select 'Use same configuration for all items' if he wants to reflect same info across.

I have save and exit button which will save the data and exit from the journey.**Next ** button will take the user into next category not the next items

So the question is how do I save data for item 1? Do I need to show a message when user selects item 2 from the Drop down? Or just auto save the info and prompt the message when a user selects another item?