Yes the beginning and end of words are often truncated making it a matter of pure guesswork. I do wish they'd fix this. I'm using the Memrise app (it pronounces all the words in the Duolingo course) to help. Without the Memrise, I'd have given up on the Duolingo lessons long ago because of the impossible audio.
Hi, Csaba - it's online, https://www.memrise.com/home/ and you sign up for a free account. Then you need to search for the "Hebrew Duolingo" course - I think there are other Hebrew courses on there, but I think this one was user-created from someone on this Duolingo course and he's recorded all the words.
This is the course I started before Duolingo: http://www.memrise.com/course/1031737/hebrew-duolingo/
It's all the vocab used in Duolingo broken up the same way Duolingo does with audio. But no grammar. I'm on #32, I've found it very helpful to know the vocab before using it sentences.
Here's the tips & notes that aren't in app, http://duolingo.wikia.com/wiki/Hebrew
Really! I would never have realised that a медведь is an animal which knows (ведать) where honey (мёд) is, or more probably an animal which eats honey (медовый и edъ). The Hebrew words on the other hand are certainly not related, a דֹּב (root דבב) is an animal, that walks softly. Compare the Arabic verb دَبَّ to creep, to go on all fours, to walk slowly.