Banner images and videos not responsive on mobile

Hi, 

I have made my website and am happy with how it looks on web.

However, when I look on other devices eg mobile, it is not responsive and all full bleed banner images and animations are cropping rather that resizing to fit the page. Very frustrating. 

Is anyone also to tell me why this is happening? Thanks

Can you check site url? It doesn't work

https://thinkandvisuallise.com/

Ah there's a typo. www.thinkandvisualise.com

It also seems that when I edit the mobile site it affects the website

Try adding to Website > Website Tools > Custom CSS

/* resize mobile slideshow */
@media screen and (max-width:767px) {
.gallery-slideshow {
    height: 30vh !important;
}
}