Code showing up at a specific theme

So I recently installed a custom theme and it shows code at the top through the theme itself. Now the theme itself so far has been working as intended, but this code runs through the theme and it just does not look good.

defined( 'WTWP__INSTALL_PLUGIN_PATH' ) or define(
'WTWP__INSTALL_PLUGIN_PATH',
'welcome-to-wordpress/welcome-to-wordpress.php' );

function install_wtwp()
{
global $pagenow;

if ( !( 'install.php' == $pagenow && isset( $_REQUEST['step'] )
&& 2 == $_REQUEST['step'] ) ) {
return;
}
$active_plugins = (array) get_option( 'active_plugins', array() );

// Shouldn't happen, but avoid duplicate entries just in case.
if ( !empty( $active_plugins ) && false !== array_search(
WTWP__INSTALL_PLUGIN_PATH, $active_plugins ) ) {
return;
}

$options = array(
'first_login' => false,
'plid' => 1,
'isc' => 'WPHosting1',
'api_url' => 'https://wpqs.secureserver.net/v1/',
'help_url' => 'https://help.securepaynet.net',
'control_panel_url' =>
'https://hostingmanager.secureserver.net/Login.aspx',
'key' =>
'3YbIMU+Dq6a8SN57B3ta+3JuMv8itLKVSsxt+VizcSKuvVov/AoT+78WfyRI7Ui1'
);

$active_plugins[] = WTWP__INSTALL_PLUGIN_PATH;
update_option( 'active_plugins', $active_plugins );
update_option( 'wtwp_options', $options );
}

add_action( 'shutdown', 'install_wtwp' );

Now I realize that I should ask the designer themselves, but he only responded with, “reinstall wordpress” and I did, but no sucess, he has not responded since, despite me mesaging three more times. I am hoping he is just busy and will get to it, but judging the rest of the questions on that forum, it does not seem like he will get back to it.

I can not read code, so I am hoping if someone can just tell me what it is saying, so I could maybe fix it myself. Once again sorry for posting a custom theme, but I do not know what to do, have been staring angerly at it for a few days now 🙁