I use Opencart for my main activity. And I am regularly updating Opencart that's why if there are new fields to translate quickly.

From the default installation (in English)

Navigation: Go to System -> Localization -> Languages

2 - Click the Add New button

3 - Enter the following values:

Language Name: German Code: de-DE Local: from, de-DE, de_DE.UTF-8, german

Status: Enabled

Sort Order: 1

4 - Save changes

5 - Navigation: Go to the topic System -> Settings

6 - On your store Store Name, Edit then click on the Local tab and change the settings of Language and Administration Language for German

7 - Save changes

8 - Installation completed

Locale Setting de,de-de,de-DE,de_DE,german,de_DE.UTF-8,de-de.UTF-8,german.UTF-8