All products sold in Germany must come with an understandble German instruction manual. Technical authors like me know,

• what content belongs into such a manual,
• the kind of "langauge" it should be written in, and
• how the layout should look like,

in order to make the consumer accept and understand the manual. Only that provides that the product will be 100% usable for your customers.

According to German law every product itself is faulty if its manual is faulty. Then the consumer can return the unit to the reseller. That does not suit you fine, does it?