Hello,

Sorry it is not our theme issue, To ensure optimal responsiveness, using different images for different devices is recommended. High-resolution images may not fit well on mobile screens. For tablets, aim for around 768px width, and for mobile devices, around 375px width is suitable.

In the slide settings in the bottom of the slide page, upload distinct images for various devices and select the background image position.
Screenshot for clarification:
https://ibb.co/v1g09JG

Best Regards.