Hi Josep.

Looks like you do not understand how the page layout is arranged. There is no left margin that you can configure. The left and right margins are always the same, since the entire content of the page is located in the .container that located in the center and having a maximum width of 1140px (in your case). Also .container has left and right margins with "auto" value, that makes it sit in the center of the page.

If you set up the left margin via CSS, I do not think that you will like the result.

Example (entire site will shift to the left):

If you apply the settings suggested by Ofi (sorry Ofi), it will also be a dubious result.

So, in order to achieve what you want, you must take out the menu module beyond the main container. To do this, you will need significant CSS skills. You can understand how it works if you explore the Fixter template through the browser code inspector

I asked a similar question for the 'left' Helix module postion found here

Hi Joe.

I do not think that you got a qualitative solution in that topic. This is a crutch that creates more problems than solves. Check this solution when changing the browser width and I think you will understand that it is very bad. I think your site twisted for one side.

The width of the columns is configured in the Layout Builder and has standard values from Bootstrap in percents. If you need an individual setting of column width in pixels via CSS you must take control of CSS all the layout and configure all other columns as well through CSS. Since, all this depends on the width of .container too.

If your site uses HU and you have one left column, сode in your case should be approximately such

#sp-left {
    width: 300px;
}
#sp-component {
    width: auto;
    flex: 1;
}