I want to get:
- Order ID for the current user;
 - All product variation ID from the current users cart;
 - Prices for product variations;
 - Images;
 - Titles;
 
I have the following:
$store_id = 1;
    $order_type = 'default';
    $entity_manager = \Drupal::entityManager();
    $cart_manager = \Drupal::service('commerce_cart.cart_manager');
    $cart_provider = \Drupal::service('commerce_cart.cart_provider');
    $store = $entity_manager->getStorage('commerce_store')->load($store_id);
    $cart = $cart_provider->getCart($order_type, $store);
    if(isset($cart)){
        $itemNum = count($cart->getItems());
        ($itemNum > 0) ? $variables['items_in_cart'] = $itemNum : '';
    }
        $cart .= 'Subtotal: '.$cart->getSubtotalPrice();
        $cart .= '<br>Total price: '.$cart->getTotalPrice();
        $cart .= '<br>Created: '.$cart->getCreatedTime();
        $cart .= '<br>Customer id: '.$cart->getCustomerId();
        $cart .= '<br>Email: '.$cart->getEmail();
        $cart .= '<br>IP address: '.$cart->getIpAddress();
        $cart .= '<br>Item num. in cart: '.$itemNum;