Hello,
We recommend using images with a size of 1920 x 640 pixels for your slides.
To optimize the experience across different devices, it’s best to use different image sizes for desktop and mobile.
You can adjust more settings by following these steps:
Navigate to Slides > Edit Slide.
Scroll down to the bottom of the slide editor.
Check the Slide Settings section, where you can configure different images for various devices and set their position: https://ibb.co/9bpLVTr
Best Regards,