Having a little issue with the theme.
Made it a bit wider because i think it's too narrow for bigger screens nowadays. I have news in center, but it's not dynamic with the expansion of the theme. Where do i fix this ??

The theme use Bootstrap 3 Framework and fixed container. The frame has class container (fixed width) or fluid-container (full width). Study the grid System of Bootstrap. Link: -link-
I think if you add the fluid-container in theme.php and max-width: anything.px in style.css, it will work normally.

Thx for your reply
I'm not an expert on this, but i'm using e107 v1 and is this theme running on Bootstrap 3 ?

This theme made for v1 and v2. If you use v1, download the theme from v1 folder.(why do you use v1, v2 better and modern).
V1 is old. I don't remember how I made the theme.
so...I think, need play with these style items:

#container {
	width: 960px;
	margin: 14px auto 0 auto;
}

#content {
    overflow: hidden;
    float: left;
    width: 460px;
    margin-left: 235px;
}

#sidebar-primary {
  overflow: hidden;
	float: left;
  width: 220px;
  margin-left: -695px;
}

#sidebar-secondary {
    overflow: hidden;
	float: right;
    width: 220px;
    margin-left: 15px;
}

#footer-menus { width: 960px; margin: 0 auto; }
.footer-menu-box { width: 225px; float: left; margin-right: 20px; }

Thx Fizi

I use v1 because many of my plugins does'nt work in v2.

I have played with all your suggestions and it worked only on side menu's, top and bottom. Nothing in center block where newspost are. Still the same size.

See attached file

How I wrote the center area is:

#content {
    overflow: hidden;
    float: left;
    width: 460px;
    margin-left: 235px;
}

It is responsible for the center area. I suggest you see with the firefox where the problem and update in the style.css file.