Removing ALL content padding/spacing from theme

I am trying to remove the space between: 1) The whole site and the background --> have been able to modify this by setting .site width to 100% 2) The text of my posts and the whole site container --> I am using #main padding = 0px but there is still some extra space between the post text and the main site container that I am not able to remove, even if the #main width is set to 100% I was trying to follow this answer but I don't understand why they are using a #primary element https://catchthemes.com/support-forum/topic/how-to-change-body-width/ Please help, I want to maximise the space for my text, so don't want any hidden padding please.