NB: This question is addressed to those learners of German as a foreign language who have faced, and overcome, the problem described here.
My fluency with numbers lags far behind my fluency with the rest of spoken German. More precisely, this fluency gap shows only with numbers greater or equal to 20. (Of course, the root of my problem is the inversion in the ordering of the units and the decades.)
This fluency gap is wider for aural comprehension than for spoken production (but this is because my spoken production is all-around much weaker than my listening comprehension).
What's worse, I'm discovering that even though my general listening comprehension of German keeps improving steadily, my comprehension of numbers has not improved at all. As a result of this uneven development, when I now listen to standard spoken German (e.g. the evening news), I perceive numbers as short stretches of gibberish in a stream of otherwise clearly understable speech.
In other words: listening practice is not working when it comes to numbers (even though it's working for the rest of spoken German).
To be clear: (of course) I understand the rules for "sounding out" numbers in German perfectly well, and, with enough time, I can decode the number words, but at a rate that is 10x slower than is required for understanding speech spoken at a normal rate. In other words, knowing the rules only allows me to decode, a relatively slow process; something more must happen in order for me to understand these numbers instantly, in the same way that I understand everything else.
Does anyone know how to overcome with this problem?
EDIT: to be more precise: does anyone know of a tool/app or specific technique to overcome this problem?
If anyone is still unclear of what I mean by the difference between "decoding" and "listening comprehension" (at a normal spoken rate), I still remember when, upon hearing the word Kühlschrank, I would have to decode it into "cool + cupboard = fridge". Now, after hearing a lot of spoken German, which has included plenty of mentions of it over time, when I hear the word Kühlschrank in spoken German, not only I don't do this decoding starting with translating kühl and Schrank; I don't even think of the English word fridge. I just know what Kühlschrank is referring to as soon as I hear the word. No decoding or translation is involved anymore. This example is pretty representative, and it tells me that my listening comprehension is improving in general (i.e., I am practicing effectively, it's paying off, I don't have a general neurologic deficit, etc.). So my problem is very specific to numbers.