Hello,

This can no tbe done thru css. You will need to edit the faq file. Please go to vc_templates/faq.php and find this block:

  $output .= '<div class="accordion-group '.esc_attr($sort_classes).'">';
                        $output .= '<div class="accordion-heading '.( ($i == 1)?'in_head':'' ).'">';
                        $id = rand(0, 50000);
                            $output .= '<a class="accordion-toggle" data-toggle="collapse" data-parent="#accordion'.esc_attr($nr).'" href="#toggle'.esc_attr($id).'">';
                                $output .= get_the_title();
                            $output .= '</a>';
                        $output .= '</div>';
                        $output .= '<div id="toggle'.esc_attr($id).'" class="accordion-body in'.( ($i == 1)?'in':'' ).' collapse ">';
                            $output .= '<div class="accordion-inner">';
                                $output .= get_the_content();
                            $output .= '</div>';
                        $output .= '</div>';
                    $output .= '</div>';

Edit to this:

 $output .= '<div class="accordion-group '.esc_attr($sort_classes).'">';
                        $output .= '<div class="accordion-heading in_head">';
                        $id = rand(0, 50000);
                            $output .= '<a class="accordion-toggle" data-toggle="collapse" data-parent="#accordion'.esc_attr($nr).'" href="#toggle'.esc_attr($id).'">';
                                $output .= get_the_title();
                            $output .= '</a>';
                        $output .= '</div>';
                        $output .= '<div id="toggle'.esc_attr($id).'" class="accordion-body in collapse ">';
                            $output .= '<div class="accordion-inner">';
                                $output .= get_the_content();
                            $output .= '</div>';
                        $output .= '</div>';
                    $output .= '</div>';

Save changes.
Keep in mind that this change will be overwritten from the next theme update you take, so we recommend to save a copy of the edited file.

Best regards!