Question about border length

Hello, im trying to find out how to make my bottom border of section a be smaller in length compared to section, i tried using margin’s and paddings but it changed size of whole section instead.

Please be more specific on what the issue is. may be post a picture of the issue if its hard to explain

Never mind, i checked out my previous tribute page and i found out the way it could work instead. I was talking about changing size i.e. length of a border of a box/container/section/header or what ever.