Sometimes after Categories or Portfolio items deleting you can get this error (White Screen or “Formatting error”)
This error says about NULL link which is stayed in the “Banner” shortcode after Categories or Portfolio items deleting.
Solution: go to the Front page, click on the banner shortcode and click “Save”

To make any changes to the theme files use a child theme, or when you update your changes to the theme files may be lost
Child Theme is included in the main archive
Child Themes documentation in WP codex

Banner Slider Settings

General
- Content stretch – Stretch content row
- Height – Set max height block
Slider Settings
Elements
- Mouse on bottom – Show or Hide button scroll to next block (#1)
- Social buttons – Show or Hide social links (#2)
- Social buttons align – Set social links position
- Social buttons color – Choose social links color
Social Links
This option is responsible for displaying social icons. By default, links are taken from “Luxa Theme > Theme Options > Social Links“, if you want to use unique links go to the tab “Social Links”.
Banner Item Settings

General
- Background Image – Choose background image (#1)
- Background Video url – Type Video url for background
- Background Overlay – Set ‘On’ if you want overlaed background. In tab ‘Background Overlay’ you can set color and gradient overlay
- Sub Heading – Type sub heading (#2)
- Heading – Type heading (#3)
- Link – Type url and link text (#4)
Customizing
- Content Align – Set content align
- Content Color – Select slide content color
- Heading Size – Select heading size from
h1
to h6

One Screen Scroll Settings

General
- Social buttons – Show or Hide social links (#1)
- Social buttons align – Set social links position
- Social buttons color – Choose social links color
- Navigation Dots – Show or Hide navigation dots (#2)
- Mouse on bottom – Show or Hide button scroll to next block (#3)
Social links
This option is responsible for displaying social icons. By default, links are taken from “Luxa Theme > Theme Options > Social Links“, if you want to use unique links go to the tab “Social Links”.
Screen Item Settings
- Background Image – Choose background image
- Container Stretch – Stretch content row
- Content Color – Select content color

One Page Horizontal Scroll Settings

General
- Navigation Dots – Show or Hide navigation dots (1)
- Mouse – Show or Hide button scroll to next screen (#2)
- Social buttons – Show or Hide social links (#3)
- Social buttons align – Set social links position
- Social buttons color – Choose social links color
Social links
This option is responsible for displaying social icons. By default, links are taken from “Luxa Theme > Theme Options > Social Links“, if you want to use unique links go to the tab “Social Links”.
Item Settings
- Side Image – Choose Side Image
- Width – Type image width
- Offset Right – Type image offset by right side

Contact form 1
<div class="contact-form"><div class="input-row">[text f-name class:style1 placeholder "Full Name"]</div><div class="input-row">[text email class:style1 placeholder "E-mail"]</div><div class="input-row">[text subject class:style1 placeholder "Subject"]</div><div class="input-row"><label>Message</label>[textarea message class:style1 x6]</div><button class="button-style1" type="submit"><span class="d"><span></span></span><span>Send</span></button></div>
Contact form 2
<div class="contact-form"><div class="input-row">[text f-name class:style1 placeholder "Full Name"]</div><div class="input-row">[text email class:style1 placeholder "E-mail"]</div><div class="input-row"><label>Message</label>[textarea message class:style1 x6]</div><button class="button-style1" type="submit"><span class="d"><span></span></span><span>Send</span></button></div>
Subscribe Form
<div class="subscribe-form"><div class="input">[text email placeholder "E-mail..."]</div><button class="button" type="submit"><i class="base-icon-envelope"></i></button></div>