Hi henning!
you wrote
"I´ve allready repleaced the gaskets and seals with the Louis-Kit. And
If i remove my gas tubes nothing gets lost. "
if the engine stops and the suction pressure diminishes, the fuel valve closes.
so your carburetors are not faulty if you lose gas overnight, but first of all the fuel valve. check that again please.
if you suck at the small tube, the fuel flows out the larger one.
"The leak MUST be inside the Carburators (but where?), there is no other place possible."
if this were the case, then the valve that is closed by the fuel floats inside the foat chambers is the nuisance.
the valve seats are probably worn, so echange tose first and check that they clos properly by blowing through the fuel pipe and lifting the float body.
the valve must close then..
NOTE: the level at which total closure is obtained is shown on the technical pages..
https://www.tr1.de/tr1/tech_info/page3e.htm ,lower picture
Regards, Klaus
P.S. maybe you lose fuel overnight because you go riding in your sleep?
(I've heard of sleepwalkers but this is ridiculous)