language display to button links

my forum had been down due the general problem
Now it's working properly, but it's slightly different.... I have corrected some display problems, but there's one I can't do anything about it.
Before the forum got down, all the button links like "Post" "Edit" "New topic" etc were in English, but now everything's in French!!!! Please note that the default language of the forum is set to Greek. Is there a way to turn it back to English or even Greek?

try to restore your back-up