Dear Sannick,
Please follow the instructions below to change the slider images.
Dashboard -> Appearance ->Featured Section Options ->Enable Feature Section ( Check the box)
Feature Slider Selection => Select Slide of Slider : Here you can choose different pages for slider.
Make sure that you have demo content uploaded.
Yes, I did it but it’s still showing the background image I don’t want. It changes the text but not the image, I want to upload a different image. Thank you in advance.