Found one typo by me: 'unknownName' => 'Ombekende productnaam', Should be: 'unknownName' => 'Onbekende productnaam', To be able to see if all is correctly translated i have to see it implemented on the pages it's meant for, but so far it looks ok
Added. I'm not sure if Microsoft JhengHei font is for Japanese, but seems that it works. Please check.
It works fine don't worry Japanese writing is based on Chinese (but at the same time hugely different) This font is ok and even looks better than default ones (such as MS Mincho)