> One weekend is not what I'd call "a lot of opportunities". If you think it is then we're discussing different levels of fluency. I'm quite conversational in German

I fully agree with you, I was at a beginner's level on that occasion. Yes, if you are conversational then it's not going to change much (from your original post it seemed you barely spoke German)

And yes, the way to progress from conversational to the upper levels is mainly through classes

> but they don't actually like German (it's something of a foreign language too compared to dialect)

Ah that's true. Nobody speaks Hochdeutsch on everyday life. And Schweizerdeutsch is weird