In my limited experience, I find that while you have to have vocabulary in order to be able to read a language, and you have to have heard it in order to be able to comprehend it when people speak, let alone be able to speak it yourself, you have to ignore the individual words when they speak quickly, and just let the flow of the words wash over you. For sure, many, and initially most, of the words will be completely lost, but over time they will become recognized. You will not be able to translate -- certainly not, quickly -- but you will be able to recognize. And with that recognition comes comprehension.
Forgive me if I've just discovered that the sun rises in the east.