Great resource, thanks a lot! I think this is really the stuff you can't learn in high school education and have to learn by yourself. There our teachers are native Germans as well and while they are probably better than the average second language English learner they can't be perfect either.

In Chinese the "x" would be pronounced like that: https://en.wikipedia.org/wiki/Voiceless_alveolo-palatal_fric...

So not really a "sh-" either, but English doesn't have that sound at all I believe.