It works Fotis, thank you! But I inserted the code max-width: 1004px; directly on the styles.less file, I never used the visual editor so I'm more at ease messing directly with the file system. :roll:
I tried the first one
but didn't work on my custom design.
Its all the same. Its simpler via visual editor cause you are editing for sure your custom css file . You dont have to look though numerous files.
I would add this to css not less but then again it makes not that big of a difference. LEss is for css variables more . This is why custom css tab in visual editor is the connection to the theme's css style file.