In general, the spoken sentences are hard for a beginner. When I compare to the Spanish course, or Welsh or Catalan, it's hard. I speak Spanish ok so I'm not surprised I find that easier to understand, but it's spoken a tad more slowly. I don't know a word of Welsh or Catalan, yet, but those are spoken a little more slowly, easier for beginning learners. Also, Spanish sounds like it's spoken by a person. Czech is synthetic, put together from individual bits and pieces spoken by a person (I assume). All in all, I find the Czech course a lot more difficult than the others. I use a book ("Czech", by James Laughton), to make sense of it all. y Nevertheless, I appreciate the effort put in the course by all who contributed.
I'll jump in late and say I definitely hear the a after the e at the end of muž. I want to say that czech is amazingly phonetic and clear. And of course you need extra resources, like online dictionaries and Naughton's two books. A great merit of the Duo system is the motivation to keep reviewing and re-listening. [Now, in contrast, the russian language has shifting stresses...]