If one of our programs starts in the wrong language, the reason are the settings of language in macOS. Our programs are always available in two languages (English and German), some apps are also has more than two languages. When a program is started, it reads the languages settings in macOS according to the sequence (see figure below) and compared with the languages of the started application. As soon as a match occurs, the application uses this language.

 

As shown in the example below, the languages English, French, Spanish and German are available in macOS. Start now, for example. the "Contract Manager", which supports the languages English, German and Dutch, the program searches for the first suitable language and in this case first finds the language "English". Thus, the contract manager is started in English.