Armin wrote:
And i told you, you find George only in 1850 and 1900 he can not be in Germany in 1860, 1870 and 1880. Same procedure with his boys nothing at all in 1910, 1920 and 1930.
Regarding your census searches: This low rate of successful returns suggests that perhaps the family (or key members of it) left the NY region at some point after 1850. Are you also searching that particular name (to include variants) across the 50 states, as opposed to just NY? There is the additional possibility that the family left the NY area and settled elsewhere for a few or even many years, then returned to NY at an undetermined point later on. This might account for a full generation or more "missing in action", and consist of the entire family unit or simply members of it. These are not "out of the question" scenarios, in fact they happened far more often than one might suspect. Resettling north into Canada either temporarily or permanently would not be out of the question either.
Sometimes such researches are really not easy. How easy would it be here in Germany to go to the church and look into a churchbook!!!!!
The sheer size of the 50 states as a collective constitute more of an empire than a country truth be known, so you have your work cut out for you once your search parameters widen. It's all part of the wonderful world of American genealogy Armin! 
If the federal censuses were not indexed to allow for a modicum of quick pointers and indicators, many would be groping in the dark far more often, particularly when it comes to those "little known" family lines or collateral branches. There are many many reasons why census searches can come up empty, but none will be more futile than those being conducted in the wrong area to begin with when they're based on prematurely 'fixed' ideas (like where the family "should" be). So... do you know for certain these Hattorfs were residents of NY for all these years? If not, and once the well runs dry, expanding your search horizons may be your next best course of action. This could take you next door to New Jersey, or clear to the west coast if there was a lure for gold. Or alas, anywhere in between.
Jb