On German keyboards the locations for the keys [Y] and [Z] are switched. Is there any option to reconfigure these, or do I have to switch to the English keyboard layout to play Aqua Kitty?

Try this - http://www.omega-com.pl/kbdkaz.htm

Or use the MSKLC provided by Microsoft: http://msdn.microsoft.com/en-us/goglobal/bb964665.aspx

Nice idea to just remap all the keys for Aqua Kitty :D but my first thought was to have "less" trouble than switching layout all the time - and this would imply switching layouts. Altho being able to remap all keys freely might even be worth it.

However, maybe someone knows a way to tip the edge within the game?

AFAIK you can't remap keys in the game for keyboard, only for controller - https://steamcommunity.com/app/263880/discussions/0/540732888847808661/#c45350791655335521

But maybe you can use this - http://www.autohotkey.com/