Slider Not Responsive?

Hello,
When I view slider on my desktop it look fine, but when I view on mobile phone the length of the slider is cut off and doesn’t look right cutting off wording and everything. I thought this was supposed to be responsive?? How do I fix this? I don’t know if this matter but currently I am using the slider as just one placeholder image, kinda like a header. Hope to get help real soon on this, thanks!