I can do the R´s
(in finnish...and in italian, too
...though I would not need them for my own language. They exist in german, depending on which area you come from, though, but the dialects were never an issue (except for some jokes) in our country and everyone pretty much speaks the "common" german, and dialect in private then, if they like. But the dialects don´t separate "classes", they are strictly regional.
Fortunately where I live the dialect is not very strong and since my parents are not born here, I have adapted only a little bit, which means, I am easy with common german.
I heard it can be difficult for foreigners, like exchange students for example, if they end up in an area with strong dialect where things in everyday life don´t sound like they learned it at school.
The original thought of this thread I noticed at myself, too. That when I speak not my own language for a while, or even while I am learning something, I start to think in different constructions. Then my german deteriorates. Couple of times I almost adressed my parents in english