Language name in prestashop URL

my prestashop base site URL is - www.7color.eu. Some urls are showing in this way -

http://7color.eu/lang-en/12-t-shirt.html

http://7color.eu/lang-en/5-gift-item

http://7color.eu/lang-en/content/4-about-us and so on

But it was not like this. "lang-en" part was not in开发者_Go百科 it. i don't understand when and how did it happen. Now i cannot remove this part. i tried to edit htaccess or re-generate it from admin. but no luck. i want the urls like -

http://7color.eu/12-t-shirt.html

http://7color.eu/5-gift-item

http://7color.eu/content/4-about-us etc.

How can I do this? i need urgent help please.

I think perhaps it has to do with enabling the nice URL strings.