Slider Factory and problem full windows
I have also found and already reported Jürgen.
Yes, thanks, I'm already aware of the issue. Unfortunately it seems there is yet no CSS-only solution possible because current browsers act erratic when using vw and vh units together with calc(), which are all CSS3 features and support is still rather new.
How do How to stretch a text block?
What type of section is this in your example?
E.g.: If it is a Slider Factory slide, the large padding is to make room for the slider navigation and it is defined in the CSS class gpSlide which is applied automatically to all first-level elements inside a Slider Factory's Wrapper. In this case you could overrule this by adding padding:0; as a style attribute via Section Attributes. In some cases it might need padding:0!important;
In other cases it might be margin instead of padding, or both.
Depending on the plugin used, there may be cases where you cannot access the text box itself directly via Section Options (e.g. the Caption of a Responsive Image). In such cases you will have to find the causative CSS and overrule it with your own styles, e.g. via Layout Manager or by editing your theme's style.css/less/scss. Right click -> Inspect Element will help you to spot the declaration and location of the causative CSS.
Ok, so we have a Section Combo with a Parallax Image section acting as background and a Text section in the foreground, both inside a Wrapper.
You might want to remove the class parallax-image-caption and replace it with gpCol12 or col-xs-12 by editing the Section Attributes of the inner Text section.
This will remove the horizontal and vertical centering of the section inside the wrapper and thereby the side margins caused by the centering.
Hope this helps and that it is actually the cause.