create_menu_link.php

<?php
// Programmatically create and translate menu links.
use Drupal\menu_link_content\Entity\MenuLinkContent;

$menu_item = MenuLinkContent::create([
  'bundle' => 'menu_link_content',
  'langcode' => 'en',
  'title' => 'My menu link',
  'description' => 'My description.',
  'menu_name' => 'main',
  'link' => [['uri' => 'internal:/taxonomy/term/15']],
  'parent' => 'menu_link_content:c8859c9c-a550-45a9-a705-5d032dee525c',
  'weight' => 0,
]);
$menu_item->save();

$menu_item_es = $menu_item->getTranslation('es');
$menu_item_es->title = 'Mi enlace del menú';
$menu_item_es->description = 'Mi descripción.';
$menu_item_es->save();

create_node.php

<?php
// Programmatically create and translate nodes.

use Drupal\node\Entity\Node;

$node = Node::create([
  // The node entity bundle.
  'type' => 'article',
  'langcode' => 'en',
  'created' => REQUEST_TIME,
  'changed' => REQUEST_TIME,
  // The user ID.
  'uid' => 1,
  'title' => 'My test!',
  // An array with taxonomy terms.
  'field_tags' =>[2],
  'body' => [
    'summary' => '',
    'value' => '<p>The body of my node.</p>',
    'format' => 'full_html',
  ],
]);
$node->save();
\Drupal::service('path.alias_storage')->save("node/" . $node->id(), "my/path", "en");

$node_es = $node->getTranslation('es');
$node_es->title = 'Mi prueba!';
$node_es->body->value = '<p>El cuerpo de mi nodo.</p>';
$node_es->body->format = 'full_html';
$node_es->save();
\Drupal::service('path.alias_storage')->save("node/" . $node->id(), "mi/ruta", "es");

create_taxonomy_term.php

<?php
// Programmatically create and translate taxonomy terms.

use Drupal\taxonomy\Entity\Term;

$term = Term::create([
  'vid' => 'sport_activity',
  'langcode' => 'en',
  'name' => 'My tag',
  'description' => [
    'value' => '<p>My description.</p>',
    'format' => 'full_html',
  ],
  'weight' => -1
  'parent' => array (0);
]);
$term->save();
\Drupal::service('path.alias_storage')->save("taxonomy/term/" . $term->id(), "tags/my-tag", "en");

$term_es = $term->getTranslation('es');
$term_es->name = 'Mi etiqueta';
$term_es->description->value = '<p>Mi descripción.</p>';
$term_es->description->format = 'full_html';
$term_es->save();
\Drupal::service('path.alias_storage')->save("taxonomy/term/" . $term->id(), "etiquetas/mi-etiqueta", "es");