I can't find this as an existing post so here goes! I am enjoying the course very much but I am battling with knowing whether my actual pronunciation is correct. Is there a way of checking this and actually speaking Greek. I currently work on a tablet.
Also, I forgot to point you towards Forvo. It's an awesome site - you should find recordings of all the most common Greek words on it. It's not very useful for whole sentences, but if you want to check your pronunciation of individual words, it's fantastic. Much better than Google Translate (which is my backup if I can't find what I'm looking for on Forvo).
Not as such - I think some of the other Duo courses have speech recognition, but not Greek (not yet, at least - it is still in Beta).
I babble constantly when studying Greek - I try to vocalise as much as possible - and I don't think my overall pronunciation is too bad, although my δ and my γ are often a bit off. If possible, I'd definitely recommend trying to speak out loud everything you hear or read; you should manage to get most of the pronunciation to a reasonable standard simply by osmosis and practice.
If you're willing to pay for it, I've heard lots of good things about Italki (though I've never used it myself). It's a website that basically pairs you up with a language teacher (https://www.italki.com/home). I think you could just buy a few lessons if all you wanted to do was check your pronunciation.
Alternatively, there are a lot of very friendly and helpful native speakers here, and also in a Facebook group for Duo users (https://www.facebook.com/groups/1460598984233543/). If you put out a call for help, you may well find someone who is willing to Skype you or to talk to you over the phone.
Good luck and happy learning!