Elementary Vietnamese comes with an audio CD. The back of the book has a bunch of minimal pairs that you can read and listen at the same time. Listening to this over and over was huge for my pronunciation and listening, especially for the subtle differences between tones like U and Ư. Native Vietnamese speakers say that my pronunciation is very good and I fully credit listening to the tones in this book over and over for a full month. The book also has good grammar lessons.
Doesn't matter where you live, you can online/Skype/Zoom with teachers from anywhere in the world. If you can't find any teachers in Hoa Binh, easy enough to find someone in Hanoi to do it.
The best book for learning Vietnamese I've found is
https://www.amazon.com/Elementary-Vietnamese-tieng-Vietnamese-Included/dp/0804845328
Not sure how easy it is to get in Vietnam, though. It's the only one I've seen that has good technical explanations.
If you are able to, you should definitely get a textbook (one that comes with online audio) or find a more in depth resource than duolingo.
Colloquial Vietnamese is decent I’ve heard and also this one has decent reviews: https://www.amazon.com/Elementary-Vietnamese-tieng-Vietnamese-Included/dp/0804845328/
I've been using this book called Elementary Vietnamese. I can speak Vietnamese casually as well, and I feel like this book has helped to fill the gaps in my Vietnamese grammar and gave me a better understanding of Vietnamese pronunciation. There are a lot of drills to practice with as well, but they don't have the answers. So this might be best for those who can already speak Vietnamese because I felt like when I did the exercises, I could read the sentences and "tell" that it sounded correct.
Assuming you're at a basic level, Elementary Vietnamese 3rd addition has been serving me well. Cost about $21. It's geared to English language speakers though, so not sure if it fits your criteria.
https://www.amazon.com/dp/0804845328/ref=cm_sw_r_cp_apa_i_isRyFbWT2VVBS