I have something like this http://example.com/en , http://example.com/fr and http://example.com/es for example I would like if I'm on this page http://example.com/en/about-us/ when I click on other language link,just to redirect to that language,but to stay on same page,for example if I click on link that will go to french site,and I'm currently on http://example.com/en/about-us/, I would like to go to this link http://example.com/fr/about-us/ if that page doesn't exists I would like to be redirect to homepage,is this possible.Hope you understand me,thank you in advance.
WPML http://wpml.org/ (Wordpress Multi Language) seems to be exactly what you're asking for and more than that. It's not free, but in this case price means quality. For example I've used qTranslate in the past, and I can tell you it was accepted mistake not to spend the money on wpml.org instead (qTranslate is free). The price IMHO isn't that high compare to the product ($29) and you get it with an unlimited license. Take a look, I'm sure you'll agree.
Just to make it clear, I'm not affiliated with them in any form.
I'm not sure is this would accomplished 100% your goals, but I normally use qtranslate for that kind of requirements.
Have a look on Multilingual Press. It is especially designed to use the features of a multisite installation for translation.