My own theme’s custom widget areas are not working

I fixed your functions.php code:

<?php

add_theme_support('post-thumbnails');
add_theme_support('menus');

/**
 * Enqueue scripts
 *
 * @param string $handle Script name
 * @param string $src Script url
 * @param array $deps (optional) Array of script names on which this script depends
 * @param string|bool $ver (optional) Script version (used for cache busting), set to null to disable
 * @param bool $in_footer (optional) Whether to enqueue the script before </head> or before </body>
 */
function theme_styles() {
    wp_enqueue_style('bootstrap_css', get_template_directory_uri() . '/css/bootstrap.min.css');
    wp_enqueue_style('main_css', get_template_directory_uri() . '/style.css');
    wp_enqueue_style('owl_carousel_css', get_template_directory_uri() . '/owl_carousel/dist/assets/owl.carousel.min.css');
    wp_enqueue_style('owl_carousel_theme_css', get_template_directory_uri() . '/owl_carousel/dist/assets/owl.theme.default.min.css');
    wp_enqueue_style('font-awesome', get_template_directory_uri() . '/font-awesome47/css/font-awesome.min.css');
}

add_action('wp_enqueue_scripts', 'theme_styles');

/**
 * Enqueue scripts
 *
 * @param string $handle Script name
 * @param string $src Script url
 * @param array $deps (optional) Array of script names on which this script depends
 * @param string|bool $ver (optional) Script version (used for cache busting), set to null to disable
 * @param bool $in_footer (optional) Whether to enqueue the script before </head> or before </body>
 */
function theme_js() {
    global $wp_scripts;
    wp_enqueue_script('jquery', 'https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js', array(), null, true);
    wp_enqueue_script('bootstrap_js', get_template_directory_uri() . '/js/bootstrap.min.js', array('jquery'), false, false);
    wp_enqueue_script('owl_carousel', get_template_directory_uri() . '/owl_carousel/dist/owl.carousel.min.js', array('jquery'), false, true);
}

add_action('wp_enqueue_scripts', 'theme_js');

function create_post_type() {
    register_post_type('slider', array(
        'labels' => array(
            'name' => __('Slider'),
            'signular_name' => __('Slider')
        ),
        'public' => true,
        'has_archive' => false,
        'supports' => array(
            'title',
            'editor',
            'excerpt',
            'thumbnail',
            'custom-fields',
            'revisions'
        )
            )
    );
}

add_action('init', 'create_post_type');

function mytheme_customize_register($wp_customize) {
    $wp_customize->add_section('themeslug_logo_section', array(
        'title' => __('Logo', 'themeslug'),
        'priority' => 30,
        'description' => 'Upload a logo to replace the default site name and
            description in the header',
    ));
    $wp_customize->add_setting('themeslug_logo');
    $wp_customize->add_control(new WP_Customize_Image_Control(
            $wp_customize, 'themeslug_logo', array(
        'label' => __('Logo', 'themeslug'),
        'section' => 'themeslug_logo_section',
        'settings' => 'themeslug_logo',
    )));
}

add_action('customize_register', 'mytheme_customize_register');


/*
 * Register Our Customizer Stuff Here
 */

function genesischild_register_theme_customizer($wp_customize) {
    // Create custom panel.
    $wp_customize->add_panel('text_blocks', array(
        'priority' => 500,
        'theme_supports' => '',
        'title' => __('Text Blocks', 'agrowinnica'),
        'description' => __('Set editable text for certain content.', 'agrowinnica'),
    ));
    // Add Footer Text
    // Add section.
    $wp_customize->add_section('custom_footer_text', array(
        'title' => __('Change Footer Text', 'agrowinnica'),
        'panel' => 'text_blocks',
        'priority' => 10
    ));
    $wp_customize->add_section('big_text', array(
        'title' => __('Duży tekst', 'agrowinnica'),
    ));
    // Add setting
    $wp_customize->add_setting('footer_text_block', array(
        'default' => __('default text', 'agrowinnica'),
        'sanitize_callback' => 'sanitize_text'
    ));
    $wp_customize->add_setting('big_text_block', array(
        'default' => __('default text', 'agrowinnica'),
        'sanitize_callback' => 'sanitize_text'
    ));
    // Add control
    $wp_customize->add_control(new WP_Customize_Control(
            $wp_customize, 'custom_footer_text', array(
        'label' => __('Footer Text', 'agrowinnica'),
        'section' => 'custom_footer_text',
        'settings' => 'footer_text_block',
        'type' => 'text'
            )
            )
    );
    $wp_customize->add_control(new WP_Customize_Control(
            $wp_customize, 'big_text', array(
        'label' => __('Duży tekst', 'agrowinnica'),
        'section' => 'big_text',
        'settings' => 'big_text_block',
        'type' => 'text'
            )
            )
    );

    // Sanitize text
    function sanitize_text($text) {
        return sanitize_text_field($text);
    }
}

add_action('customize_register', 'genesischild_register_theme_customizer');

function wpb_widgets_init() {

    register_sidebar(array(
        'name' => 'Custom Header Widget Area',
        'id' => 'custom-header-widget',
        'before_widget' => '<div class="chw-widget">',
        'after_widget' => '</div>',
        'before_title' => '<h2 class="chw-title">',
        'after_title' => '</h2>',
    ));
    register_sidebar(array(
        'name' => 'Footer Sidebar 1',
        'id' => 'footer-sidebar-1',
        'description' => 'Appears in the footer area',
        'before_widget' => '<aside id="%1$s" class="widget %2$s">',
        'after_widget' => '</aside>',
        'before_title' => '<h3 class="widget-title">',
        'after_title' => '</h3>',
    ));
    register_sidebar(array(
        'name' => 'O nas',
        'id' => 'o-nas',
        'description' => 'O nas',
        'before_widget' => '<div id="one" class="two">',
        'after_widget' => '</div>',
        'before_title' => '<h2>',
        'after_title' => '</h2>'
    ));
    register_sidebar(array(
        'name' => 'O naso',
        'id' => 'studio-text',
        'description' => 'Studia',
        'before_widget' => '<div id="one" class="two">',
        'after_widget' => '</div>',
        'before_title' => '<h2>',
        'after_title' => '</h2>'
    ));
}

add_action('widgets_init', 'wpb_widgets_init', 0);

your wpb_widgets_init function for the widget areas was inside genesischild_register_theme_customizer also there was one area outside.