I hired a private tutor for two hours per week for Chinese before a trip to Beijing. That way I could tailor the content to the kinds of things I felt I would need. It's a bit more pricey but I was very happy with the results. We worked for 2 months twice a week or an hour each time.

Finding a tutor may be more of s challenge for Greek than was Chinese but depending on where you are, you may be able to find a reasonably qualified teacher.