Google-maps – Change language forever

First of all, I recommend you to start with clearing your Google cookies, since I think it can be that Google stores your language in a cookie as well.

After your did that, head over to https://www.google.com/settings/language and select your language. Normally all Google services should be in that language by default then, but I know of some that manage languages by themselves. Like f.e. the Google Play Store.

Google provides a language setting per Google-account.

Since this page will likely be in Greek for you, I'll quote it below: https://support.google.com/accounts/bin/answer.py?hl=en&answer=32047

To change the display language for Google Accounts, you'll need to change your Google interface language:

1. Visit your Accounts settings page. (https://www.google.com/accounts)
2. Click the Language tab.
3. Use the drop-down box to select your primary language, and click "Add another language" if you'd like other options.

Once you've changed your interface language, close the browser window. Then, open your browser and visit https://www.google.com/accounts/. The Google Accounts homepage should be displayed in the language you've selected.

If the interface language doesn't match the language you selected, please clear your browser's cache and cookies (http://www.google.com/support/accounts/bin/answer.py?answer=32050) and try setting the interface language again. Note that deleting your cookies will also remove your saved settings for other sites you've visited.

Keep in mind that while the Google Accounts homepage is available in all Google languages, individual Google products may not be available in all languages.