I started learning a few months ago (also because of the girlfriend curse), I found that learning online is useless, it is confusing and actually wastes your time. Luckily I can speak afrikaans (similar to dutch) so I can pronounce most words correctly even with rolling “r”’s and the “ch” (I mean the slovak ch sound).
What I would recommend is to get this book:
Beginning Slovak by Oscar E. Swan
It really covers all the bases, however be aware that it will require a really large amount of work, and repeating exercises over and over. Remember that there are no short cuts though.
To learn how it sounds, speak to some people if you know them, or search for some steaming slovak TV channels online.
I started off well but haven’t done any work in the past month due to work commitments. I was hoping to maybe go and study in Slovakia in a language course, but I am not sure of the fees, does anyone know? I am an EU citizen.
