Yes, it’s like that in Germany: in one place they say ‘sehr’ … in the next town ‘arg’ … in Hochdeutsch ‘Flasche’, in Hamburgerisch ‘Buttel’.
The only people who understand Kölsch are the Kölner themselves and other Dutch speakers ¹ — Try listening to albums by BAP, if you want to hear what I mean.
When I arrived in Germany, I spoke no German and hadn’t a hope of ever understanding a single word of Schwäbisch.
A year later, I spoke better German than 95% of native speakers ever will.
Six years later. I spoke better German than 99% of native speakers ever will … and still hadn’t a hope of ever understanding a single word of Schwäbisch — but neither does anyone else ², so that’s okay.
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¹ Dutch is only a dialect of German anyway — not a real language at all.
² It isn’t a real language … they just make it up as they go along and pretend to understand each other ³ — but, really, how large a vocabulary do you need, when the only concepts you’ll ever express are ‘Geld’, ‘Weib’ and ‘Spätzle’ anyway?
³ À la Papa Lazarou …