[Theme: Adelle] Can't add a custom header image

Hi! Hope someone can help. I know basic coding but I’m lost here.

I’ve been trying for hours to add a custom header image (logo) to the Adelle theme.
here is the website : https://www.ptibiscuit.com
here is a temporary “logo” image : https://ptitbiscuit.com/wp-content/uploads/2013/04/cropped-ptitbiscuit.gif

I originally did not even have the plugin “Header image” in the Appearance menu>Header image. I added it in the Functions.php file with : add_theme_support( ‘custom-header’, array etc etc… Now i have the plugin but when I try to add an image with it, it doesn’t show on the website.

The theme contains a file named “ace_functions.php” and I’m guessing the solution could be in this part but I don’t know exactly how:

// ==================================================================
// Heading
// ==================================================================
function ace_heading() {
  if( get_option('ace_enable_image_logo') ) {  ?>
    <a>"><img src="<?php echo get_option('ace_logo'); ?>" title="<?php bloginfo('name'); ?>" alt="<?php bloginfo('name'); ?>" class="aligncenter" /></a>
  <?php } else { ?>

  <?php if( is_home() || is_front_page() ) { ?>
    <h1><a>" class="header-title"><?php bloginfo('name'); ?></a></h1>
    <p class="header-desc"><?php bloginfo('description'); ?></p>
  <?php } else { ?>
    <h5><a>" class="header-title"><?php bloginfo('name'); ?></a></h5>
    <p class="header-desc"><?php bloginfo('description'); ?></p>
  <?php }
  }
}

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Let me know if you need more info! Thanks!