Drupal: Multilingual SEO website
For a multilingual Drupal 7 site you could enable the Locale and Content translation modules, they are both included in the Drupal Core.

Also, you might want to check the Internationlization module and the Entity translation module.

Basically you start of by adding languages to your site, you can do this in the administration area (/admin/config/regional/language). After that you can allow content types to be translated (/admin/structure/types). When you add a node you will then be able to choose between the enabled languages.

As for SEO: you could check the Drupal SEO Tools, it has a huge list of modules that you can use.