german translation is not used

-- url of the page with the problem -- : gebrauchte.beamerstation.de
-- HikaShop version -- : 3.1.1
-- HikaMarket version -- : 1.7.3
-- Joomla version -- : Joomla! 3.7.3
-- PHP version -- : 5.6.31
-- Browser(s) name and version -- : Firefox54.0.1 (32-Bit)

Hi,
i translated everything in hikamarket and hikashop to german in my backend. But only a few words will be used in the joomla components aerea in the head are translatet in german, everything else is still in englisch. Front and Backend. And i dont understand it.
It was more than 2 Days of work for me to translate every single line. Maybe not every line is translated perfect, but it is in german now and i would fix it later if i found them on the page. But the shop dont show me anyof my translations.
How can i get to my hikashop and hikamarket in german?

Thanks for your help

thank you so much. It was the right tipp to the right time. I didnt notice the debug modus for languages in joomla but if i used it, it was just a problem of 4 little " now the 4 missing " are in and everything is in german.