It would be nice to know your age and your cultural background.
What country/culture are you comparing Germany with?
I am German and I live in Germany for some decades now. I am an Engineer with some years of working experience in Science and Industry.
Before you asked it, I never thought about that and I still don't think that statements like "I mean I see people so healthy, fit, smart, doing various sports, great in study and so on. Is it only about waking up early at 5am?!" are generally true - neither here in Germany nor somewhere else.
On the one hand: not everyone here is like that.
An on the other hand: there are many many other countries (in Europe and for sure also overseas), where many people do similar things.
So im my opinion this level of "Productivity" is not typically German.
At first, not everyone who is successful in life, gets up at 5 am. This highly depends on the person and its biorhythm. And on the other hand just getting up early will not necessarily make someone successful and productive.
Anyway, I tried to find sources for your theory.
It is true that Germany (like other countries in Europe) has a very successful history in culture, science and technology. It's a good question, if this is somehow related to the lifestyle and the "average attitude" here.
I found an interesting article from BBC News (2012) here:
German economic strength: The secrets of success
for "cultural reasons" they write:
But cultural differences are just as significant - quite simply, Germans are uncomfortable with the concept of borrowing money and
prefer to live within their own means.
"In German, borrowing is 'schulden', [the same word for] guilt. There
is an attitude that if you have to borrow, there is something wrong
with you," says Mr Kohl.
This has been particularly beneficial to Germany in recent years -
unlike its European counterparts, consumers and businesses did not
need to slash spending to cut their debt levels when banks stopped
lending during the recession.
More reasons are (according to the article) the educational system
Apprentices aged 15 to 16 spend more time in the workplace receiving
on-the-job training than they do in school, and after three to four
years are almost guaranteed a full-time job.
And in Germany, there is less stigma attached to vocational training
and technical colleges than in many countries.
"They are not considered a dead end," says Mr Woergoetter. "In some
countries, company management come from those who attended business
school, but in Germany, if you're ambitious and talented, you can make
it to the top of even the very biggest companies."
The German education system, therefore, provides a conveyor belt of
highly skilled workers to meet the specific needs of the country's
long-established and powerful manufacturing base, which is rooted in
the stable, small-scale family businesses that have long provided the
backbone of the economy.
Excerpt from: Norbert Hedderich, "When Cultures Clash: Views from the Professions," Die Unterrichtspraxis (1999): 161-65.
Another interesting source about German attitude I found is this article. It's written from a foreigner's perspective about "typically German" behaviour at work etc.
Beware: it might be highly subjective, but maybe it helps you find an answer for yourself.