Hello, @Saira,
If you use the image as the BG image for the slider + background-size “cover” you need to understand that image will be cropped on different devices because background-size “cover” works in this way https://cssreference.io/property/background-size/
You are using Slider Revolution on your site, so you have to go to Slider Revolution and edit the particular slider and then you have to go to Slide Option and under it change the BG fit as per your requirements: https://postimg.cc/TyqDpxF2
Regards 8Themes Team.