Unable to show form using controller (module)
You need define new function theme bive_page_theme before call it. You can see docs and example. In your case, you can write more code in file .module

/**
 * Implements hook_theme().
 */
function Your_Module_theme($existing, $type, $theme, $path) {
    return [
        'bive_page_theme' =&gt; [
            'variables' =&gt; [
              'form' =&gt; NULL,
            ],
            'path' =&gt; $path . '/templates',
        ]
    ];
}


and create file bive_page_theme.html.twig in folder templates of module. Clear cache and go to page.