To Horst about listening comprehension
Similar problems also happened to me while I was speaking to some Australian locals in rural area where they have strong accents to confuse my understanding in their unique Ozzie English. A point you might have be hold is to learn "standard Mandarin". I remember I watched a coverage in a Chinese news which showed a interviee having extraordinary strong accent and I suppose that many of Mandarin learners cannot recoginize what he was speaking even though he is a young man.
But anyway, like "不好意思 " I guess that is pretty universal for all language learning if you cannot catch them in a bulk. Good luck to your learning and enjoy the journey.