On-line classes, what I've observed so far, are usually a waste of time!
Even Rosetta Stone doesn't measure up. I recently on a lark, tried to imagine that I were the average monolingual Anglophone learning Polish on Rosetta, and found myself so frustrated at the lack of depth, I would have given up and demanded my money back, no kidding either.
There is Bookbox which offers countless FREE hours of listening in almost any language there is, but in terms of a serious program, I'd have to refer anybody to the series I used back in the 1990's "Wsrod Polakow", with textbook and accompanying CD Roms (3 of them).
Best damn stuff I've come across yet, because it really made things clear beyond the initial stages of mere repetition drill a la Berlitz et al. The CDs reinforced structure with listening practice, the speakers were all Polish natives apparently, and when we got to the aspect distinction, the textbook didn't gloss over things aka "It's easy, it's easy!" etc., but admitted that it takes years of practice and requires simply rote memorization after a certain point:-)
Can't recommend "Wsrod Polakow" enough. Ought to add I was studying Polish at the time through the Kosciuszko Foundation in Manhattan. tarsape@gmail.com
If you are English speaking, Pimsleur has been great for me. I have yet to use the reading and writing portion, but my verbal skills where non existent before are getting me through basic conversations.
I'm familiar with the Pimsleur series, but was not too impressed. As with Berlitz and Rosetta, there is an excess of repetition drill sans sufficient explanation of the basic structures being practiced, in the intermediate programs I looked into as well.
A single example occurs to me from that Rosetta Stone intermediate Polish I mentioned briefly the other day. In the pattern drill practicing how to say in Polish "Please bring me a cup of coffee!", nowhere is ever even hinted at the crucial difference in such an easy sentence between "przyniesc" vs. "nosic", and why the former instead of the latter would be used.
Had I relied solely on that program in order to learn Polish with zero background, I'd have been lost...and again, frustrated.
As I think of it, Poznan and Krakow probably have what you're looking for, abd!
@PolAmKrakow Yes i am an English speaker. i just started Pimsleur few weeks ago, its very good now i can understand how polish works thank you for the recommendation