Multilingual support

Hello,

I downloaded wordpress in my domain. I want to have the blog both in english and in greek. The language must change from let’s say flag in my page.

I have found some plugins but they are for translating. But what I want is that the administration will post both languages for every post. Likewise the blog’s template should be multilingual.

What is the best plugin? I tried gengo but produced an error. I didn’t create the nessesary tables in my DB.