How to get rid of gaps in my site

Site URL: https://www.bottlerocketrecording.co.uk/

Hi there,

I have a scrollable site (not sure the technical term) and I'm having issues with the gaps between the pages being too large. Is there some CSS that I can enter to change this? My template is Brine I believe. I've attached a picture to show what I mean - I'd like them to be half the size they are at the moment. 

Thanks for your help. 

Thanks so much! Have a great week.