If you want to work in another country, you also have to speak the language of that country. If you have a demanding profession, you also have to know the usual technical language, otherwise you will hardly receive adequate job offers.
For studying and participating in international congresses and for publications, English is sufficient. But if you want to talk to German colleagues and employees, you can usually only do so in German.
As a rule, German employees hardly have the English skills to be able to discuss everything that needs to be discussed in the workplace with them in English. This topic is explained clearly in the video. Those who speak German as a foreign language can choose a suitable language for the subtitles. Those who cannot follow the speed of the lecture can reduce the speed in the YouTube settings.
The sources used to produce the video in alphabetical order: