Text domain problems in functions.php. You have not included a text domain!

[ Moderator note: Code fixed, please wrap code in backticks or use the code button. ]

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Theme Info:

880x660 611k

Title
Zerif PRO

Version
1.3.5

Author
Themeisle

Author URI
https://themeisle.com

Theme URI
https://demo.themeisle.com/zerif-pro/

License
GNU General Public License version 2

License URI
license.txt

Tags
black, gray, red, white, one-column, two-columns, right-sidebar, responsive-layout, custom-background, custom-menu, editor-style, featured-images, threaded-comments, translation-ready

Description
Zerif PRO is a modern responsive WordPress Theme. It’s perfect for web agencies, digital studios, corporate, product showcase, personal and business portfolio.

Running 13352 tests against Zerif PRO using Guidelines Version: 20141222 Plugin revision: 1
One or more errors were found for Zerif PRO.

    RECOMMENDED: Text domain problems in functions.php. You have not included a text domain!

    Line 2005: <label for='<?php echo $this->get_field_id( 'color' ); ?>'><?php _e( 'Color:' ); ?></label>

    WARNING: error_log PHP error log found.
    REQUIRED: The theme uses the register_post_type() function, which is plugin-territory functionality.
    REQUIRED: Found a Customizer setting that did not have a sanitization callback function. Every call to the add_setting() method needs to have a sanitization callback function passed.
    REQUIRED: screen_icon() found in the file class-tgm-plugin-activation.php. Deprecated since version 3.8.

    Line 391: screen_icon( apply_filters( 'tgmpa_default_screen_icon', 'themes' ) );

    Line 1585: screen_icon( apply_filters( 'tgmpa_default_screen_icon', 'themes' ) );

    RECOMMENDED: could not find the file readme.txt in the theme. Please see Theme_Documentation for more information.
    RECOMMENDED: Possible variable $theme_text_domain found in translation function in functions.php. Translation function calls must NOT contain PHP variables.

    Line 688: 'complete'                        => __( 'All plugins installed and activated successfully. %s', $theme_text_dom

    RECOMMENDED: Possible variable $theme_text_domain found in translation function in functions.php. Translation function calls must NOT contain PHP variables.

    Line 686: 'plugin_activated'                => __( 'Plugin activated successfully.', $theme_text_domain ),

    RECOMMENDED: Possible variable $theme_text_domain found in translation function in functions.php. Translation function calls must NOT contain PHP variables.

    Line 684: 'return'                          => __( 'Return to Required Plugins Installer', $theme_text_domain ),

    RECOMMENDED: Possible variable $theme_text_domain found in translation function in functions.php. Translation function calls must NOT contain PHP variables.

    Line 662: 'oops'                            => __( 'Something went wrong with the plugin API.', $theme_text_domain ),

    RECOMMENDED: Possible variable $theme_text_domain found in translation function in functions.php. Translation function calls must NOT contain PHP variables.

    Line 660: 'installing'                      => __( 'Installing Plugin: %s', $theme_text_domain ), 

    RECOMMENDED: Possible variable $theme_text_domain found in translation function in functions.php. Translation function calls must NOT contain PHP variables.

    Line 658: 'menu_title'                      => __( 'Install Plugins', $theme_text_domain ),

    RECOMMENDED: Possible variable $theme_text_domain found in translation function in functions.php. Translation function calls must NOT contain PHP variables.

    Line 656: 'page_title'                      => __( 'Install Required Plugins', $theme_text_domain ),

    RECOMMENDED: No reference to add_theme_support( "title-tag" ) was found in the theme. It is recommended that the theme implement this functionality for WordPress 4.1 and above.
    INFO: iframe was found in the file google_map.php iframes are sometimes used to load unwanted adverts and code on your site.

    Line 7: echo '<iframe class='zerif_google_map' frameborder='0' scrolling='no'  marginheigh

    INFO: class-tgm-plugin-activation.php The theme appears to use include or require. If these are being used to include separate sections of a template from independent files, then get_template_part() should be used instead.

    Line 1073: require_once( ABSPATH . 'wp-admin/includes/class-wp-list-table.php' );

What is wrong here? In a less difficult explanation? What can i do to fix it? This log is from my theme-checker