Multi-lingual menu

Hello Tal,
Thank you for your answer. I tried the code but it doesn’t work. When you connect for the first time to the website the page keep blank even if the language is set in the browser.
But, actually What I need is the same kind of translation in both applications. I use Ecwid. So I would like my website to be displayed in the language set in the browser. because Ecwid translate that way automatically .
My webpage is directed to people who usually speak severals languages, So it is totally possible they understand perfectly Spanish but their browser is set in French or English: So at first if we define the local language as english but later ther browser is in french, We will have one part in english (wix) and the other part (ecwid) in french. It’s not good.

How can I do to display the language by default as the language in the browser?

Thank you very much again if you can help