The Testimonial carousel widget works like the standard Elementor widget but comes with extra settings with layout but it automatically detects ACF fields.
You find it easiest by searching for ACF Image in the Elementor Search Widget … field:
Drag the following widget icon into your section to add the widget.
After adding the widget to your section/column the following settings are shown.
The widget detects repeater fields. Selecting a repeater field will display drop downs with additional fields.
The required fields are
There are numerous settings you can tinker around with to get the carousel you want.
You have a lot of control on the layout of the carousel. Width, height, where the quote should be shown.
If your repeater has an image field you can use the Dynamic fields option on the image background so you can have a unique background image per quote.