I have found a spell checker in english:
Is there also one in german?
Try JavaScript SpellCheck. It supports a wide variety of languages including German.
Most of the application i developed, I used the key-value paired JS file for all required languages. Those translations i am received from business or i translated English to XXX language using google translator & verified those from the business. Once you have it then it is very easy to apply it into application using angular translation service.