Hi @athina_tzan, thanks for your post. I took a quick peek at the site via the read-only link, but the slider does not seem to have any images now setup.
If you were using Background Images for your slider, a good thing to keep in mind: If the image you are using for a slide is using the cover option, then if the window size is larger than the image, the image will zoom. If the window size is smaller than the image, the image will crop.
if you always want to show the full image in the slide, then I would use the "Contain" option in the Background Image settings instead of the Cover option.
I hope this helps! If you update the images and there are still issues, let me know and I am happy to take another look.
Thanks in advance!