Armoros on "[Theme: Decode] Change fonts, Greek characters."

Hi i have a slight issue with the fonts too, i have my site in 2 languages English and Greek, is it better to use Google fonts or @font-face?
If i use Google Fonts what and where i must put the code? I use the code that google provides but no luck, i want to use droid sans, but nothing change.

Thank you for any help and congratulations for your theme.