How to get table names from external DB in non public schema

I am writing a configuration entity modul in drupal 9. I want to list all tables, from an external database (postgis) in the schema called gi. The switch between the databases is no problem. I'm searching for a way, to only get the name of the table called gruenzuege to put this in a markup form.

//the form where to save the table

 $form['tables'] = [
      '#type' => 'fieldset',
      '#title' => $this->t('Tables'),
      '#collapsible' => TRUE, // Added
      '#collapsed' => FALSE,  // Added
  ];

//External Database connection

$postgis_database = array(
      'database' => $drugis_postgis_connection->getdatabase(),
      'username' => $drugis_postgis_connection->getusername(),
      'password' => $drugis_postgis_connection->getpassword(),
      'host' => $drugis_postgis_connection->gethost(),
      'driver' => 'pgsql'
  );
Database::addConnectionInfo('postgis', 'default', $postgis_database);
Database::setActiveConnection('default', 'postgis');

//example for fetching table:gruenzuege in drupal

    $results = Database::getConnection('default', 'postgis')->query('SELECT * FROM "gi"."gruenzuege"')->fetchAll();
dpm($results);

I don't understand how to query to another schema, to get only, the table names of the schema gi? It is actually the only table. Thanks for help

listing all table names in an array

$example_database = array(
      'database' => ...,
      'username' => ...,
      'password' => ...,
      'host' => ...,
      'driver' => 'pgsql'
  );

Database::addConnectionInfo('example_key', 'default', $example_database);
Database::setActiveConnection('default', 'example_key');

$result=Database::getConnection('default', 'example_key')->query("SELECT table_name FROM information_schema.tables WHERE table_schema = '" . example_schema . "';");
  $tables = $result->fetchAll();

foreach( $tables as $table ) {
      dpm($table->table_name);
      $tableNames[] = $table->table_name;
  }

Database::setActiveConnection();