For me, the male speaker is more clear than the female one. I don't know if he is new to the Android version (For a long time I've been hearing him on PC browser) but I like him being clear.
I think the problem is not with the lady but with the recordings. Hope Duo solves this as it seems a common issue.
Yes I have this problem too, especially in any situation with background noise. I have heard other Italian speakers that enunciate more clearly and have harder consonant sounds (if you've ever heard the people speaking on Coffee Shop Italian that is a good example) and that would be a much easier voice to learn from.
Your sentence as written would typically be considered incorrect except in the context of a real time exchange such as a conversation or texting/chat. This is because English does not have special verb endings to indicate the subject. In a real time conversation, the subject will be known, which is why we often leave them out when talking or texting. But without the context of the real time conversation, things can become ambiguous (who doesn't know? You don't know, or they don't know?). As such, it would be considered incorrect in any written context. Again, texting and chatting are technically written, but move like spoken language and in fact are almost their own language with their own conventions and rules. So if your asking if there would ever be a situation when that would be correct, well, it depends on what you mean by "correct"... (But it's almost always best to err on the side of more grammatically correct than less.)