Okay, it happened that there were some weird wrong codes inside the language file.
So, even thought I did the multilanguage site, it did not accepted the modules because of that issue. ( Is it possibile?
I did not even knew it may happens! ). There were missing lines, also. ( it has shown me, for example, only com_virtuemart_cart_add_to instead of add to cart because of these, after I started to work furthermore )
I uploaded manually every file, and now the site works fine. I have an English side and an Italian side.
Actually, the real solution was the multilanguage site ( like you always said, sssssssss
sorry to have bothered you! ) but It didn't look like at first because of other bugs!
I thought I was completely insane.
I'm only a chemist.
Thank you for your patience!