Sidebar properties

I´m using a hugo theme and I want to change the sidebar size but I´m having some problems with my sidebar properties, I do change it in the css file but, once I refresh the nav I don´t see any change at all, but if i inspect the sidebar and make some changes in console it works, but not when i do it in my code.
What´s happening?
how can I make those changes?

Hi there. We need to see your code in order to help. Also, what theme are you using?