Germany: really trustworthy
Of course, you have to be clean in order to be trusted.
UK: invalid or no legal force
'The contract was null, you get zero damages.'
'Their marital contract has been null and void because of decree nisi.'
UK: derogatory or vulgar term for a man's genitalia or an insult slang for being dull.
Germany: fed up with
'I feel such a dick after talking to that dick.'
UK: Japanese art using trees by making them small and tiny instead of a properly grown tree.
Germany: runt (which was actually gotten from the small dwarfed Japanese tree)
'Your kids are still like a bonsai.'
UK: very large just like a maxi skirt or a maxi dress
(Maxi is a German slang that becomes a prefix of another adjective such as maxischoen – very lovely)
'My maxi dress is making me look maxi pretty.'