There is no single official answer, because German universities use their own conversion methods. But a percentage of 75 will generally land in the satisfactory band of the German scale, not at the top and not at the bottom.
German universities grade from 1.0 to 5.0, with 1.0 as the best. The bands are: 1.0 to 1.5 very good (sehr gut), 1.6 to 2.5 good (gut), 2.6 to 3.5 satisfactory (befriedigend), 3.6 to 4.0 sufficient (ausreichend). A 4.0 is the lowest passing grade. A 5.0 means failed.
A common conversion method is the modified Bavarian formula, which maps foreign grades onto this scale. Exact results depend on the maximum grade and the minimum passing grade in your home system, so the same 75 can convert to slightly different German grades at different universities.
If you need a conversion for an application, use the method published by the university you are applying to. Admissions offices will apply their own rules in any case.
Related reading: What is a 1.5 GPA in Germany?, Is 1.5 GPA good in Germany?, and How to convert 10 CGPA to 4 GPA?

