Hi
<blockquote>1) I am testing it and seems that I risk to lose tons of articles.
When I change the menu (now I am using the Magazine Menu) should I change also the category of ALL the old articles or there is a quicker solution to save old articles?</blockquote>
This depends on how you want to organize your new template you can have same categories and you will not lost any article
you can also take a backup with akeeba first to make any change and also make a db export with phpmyadmin
<blockquote>2) I’ld like to add in home page, left column an area with blogs, like http://www.huffingtonpost.com, is it possible with the template “Nex”? Is there a module? </blockquote>
You can have it with Ja_Nex and the left position just choose as layout left – main – right