many thanks for your reply,
i've followed the first step:
1) When i went to configuration i found the MULTILANGUE option and checked both of installed languages.
2) Then i went to products and edit. A dropdown with language select appear, i cheked the second lang and change only the alias (If you don't change the alias the product will not be saved).
3) Then Save.
but if i try to change the language setting, this message appear: No (en-gb) translation product, please fill in the fields marked with Flags
shoud i install the english language?