Funny enough the uploader has made that video unavailable in Germany (OTRAG was a German company, the first private/commercial aerospace company about 3 decades before SpaceX).
Scott Manley has a video about them, and that's also available in Germany ;)
https://www.youtube.com/watch?v=ed4w4Cz5ccU
PS: GP probably meant this one (this is just the trailer of a German documentary from 2018):