Or in your site front page, in the admin bar find Edit Page ( Back-end Editor ) or Edit with WPBakery Page Builder ( Front-end Editor )
For changing size and margin, go to Theme Options > Header > Header > Logo element
You can edit this element in page builder.
This element has -380px Margin from top, you can find it in Image Styling stylekit of this element.
This element has Background Layer effect (Orange box of background), you can edit or remove it in Background Layer Stylekit of this element.
You can edit this element in page builder.
This element has -110px Margin from left, you can find it in Image Styling stylekit of this element.
This element has Parallax effect, you can edit or remove it in Advanced tab of this element edit box.
You can edit this element in page builder.
You can edit this element in page builder.
Instead Quick Contact also you can create any page and assign it.
This element has -35px margin from top, you can find it in Container stylekit of this element.
For editing menu navigation settings go to Theme Options > Header > Header > Menu Element
And for styling menus go to Theme Options > Header > Header > Menu Styles of this Row
The content of this Offcanvas is Sidebar widget, you can find the Off Canvas Widget in Appearance > Widgets > Offcanvas Sidebar