Stacking div layout - trying to make responsive

My client has sent through an Instagram Story template idea that she likes - I’ve already explained that websites will work differently and going from one device to another, it will not look the same on every screen however she’s still bent on making this work for mobile.

Looking at the design at the preset breakpoints, it looks okay - however when I actually bring it over to my real mobile (Galaxy s10) it looks absolutely terrible.

Can someone point me in the right direction on what it is that’s going wrong and how I can try to fix it?

Here is my site Read-Only