Website not responsive to PC

I’m having an issue with elements of my page which aren’t responding well when the public website is opened on a PC/internet explorer (I’m doing this on a MAC/Safari and things seem fine), or when opened on mobile / ipad.

For example, my email address entry box is no longer centered. Or, my sub-header moves just slightly above my background picture, which means it becomes hard to see.

Could you advise how to fix this issue?

https://preview.webflow.com/preview/mbastash?utm_source=mbastash&preview=0599728ee916f8594c24179064ca5ca8