Untitled

use Drupal\views\Plugin\views\query\QueryPluginBase;
use Drupal\views\ViewExecutable;

/**
 * Implements hook_views_query_alter().
 */
function your_module_name_views_query_alter(ViewExecutable $view, QueryPluginBase $query) {
  if ($view->id() == 'your_view_id') {
    // Get the user-selected values for the Country and City filters.
    $country_filter = $view->exposed_raw_input['country_filter'];
    $city_filter = $view->exposed_raw_input['city_filter'];

    // Create separate conditions for Country and City.
    $country_condition = $query->addWhereExpression(0, "node__field_venue_of_mission.field_venue_of_mission_value LIKE :country_filter ESCAPE '\\\\'", [':country_filter' => "%$country_filter%"]);
    $city_condition = $query->addWhereExpression(0, "node__field_city.field_city_value LIKE :city_filter ESCAPE '\\\\'", [':city_filter' => "%$city_filter%"]);

    // Create an OR condition group for the separate conditions.
    $or_group = $query->orConditionGroup();
    $or_group->addCondition($country_condition);
    $or_group->addCondition($city_condition);

    // Add the OR condition group to the query.
    $query->addWhereGroup($or_group, 'OR');
  }
}