If faced with this situation, I'd use my spare diaphragm pump to move the water into the tank, and would set up the appropriate electrical connections.
BTW, Does Germany use the same garden hose fittings as we do in the US?
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The US standard for the threaded portions is 3/4-11.5NH (3/4" is the internal diameter, 11.5 is the thread pitch - 11.5 threads per inch).
Help that hopes!
(Not germane to the conversation - I very much enjoyed my business/pleasure trip to Munich/München in September of 2017!
https://pbase.com/brucemac/2017septmunchen)