Submit a CPT from Frontend

Hello, I’m sending a CPT through Frontend using the code below that is in my functions.php. On the frontend registration page, I have the form. It’s working, the only problem is that after sending the form, the success message appears on a white screen, and it ends. I need this message to somehow appear below the form. It is possible? Can someone help me?

FUNCTIONS.PHP

if(isset($_POST['name'])){
    
    $office_post = array(
            'post_type' => 'office',
            'post_title' => $_POST['name'],
            'post_content' => $_POST['address'],
            'post_status' => 'draft',
            
        );
    
    $post_id = wp_insert_post($office_post);
        
        if (!function_exists('wp_generate_attachment_metadata')){
                require_once(ABSPATH . "wp-admin" . '/includes/image.php');
                require_once(ABSPATH . "wp-admin" . '/includes/file.php');
                require_once(ABSPATH . "wp-admin" . '/includes/media.php');
            }
             if ($_FILES) {
                foreach ($_FILES as $file => $array) {
                    if ($_FILES[$file]['error'] !== UPLOAD_ERR_OK) {
                        return "upload error : " . $_FILES[$file]['error'];
                    }
                    $attach_id = media_handle_upload( $file, $post_id );
                }   
            }
            if ($attach_id > 0){
                update_post_meta($post_id,'_thumbnail_id',$attach_id);
            }
    
    echo 'Message success!';          
    
    die;
}

PAGE-FORM.PHP

<form method="post" class="form-wrap3 mb-30" data-bg-color="#f3f6f7" enctype="multipart/form-data">
                    <div class="form-title">
                        <h3 class="mt-n2 fls-n2 mb-0">Preencha seus dados</h3>
                        <p class="mb-4 mt-2">Depois do envio dos dados, faremos uma análise, e sendo aprovado, sua oficina estará disponível em nossa lista no prazo de 48h.</p>
                    </div>
                    <div class="form-group mb-15">
                        <input type="text" class="form-control style3" name="name" id="name" placeholder="Office Name" />
                        <i class="fal fa-user"></i>
                    </div>
                    <div class="form-group mb-15">
                        <textarea name="address" id="address" cols="30" rows="3" class="form-control style3" placeholder="Full Address"></textarea>
                        <i class="fal fa-pencil-alt"></i>
                    </div>
                    <div class="form-group mb-15">
                        <label>Insert your logo</label>
                        <input type="file" name="thumbnail" id="thumbnail" />
                    </div>
                    <div class="form-btn pt-15">
                        <button type="submit" class="vs-btn style2">Submit</button>
                    </div>
                    <p class="form-messages mb-0 mt-3"></p>
                </form>