Both of the words are Turkish and you have no idea what they mean. Yes Kebab isnt Döner because there is even stew like meals called kebab such as tas kebabı. Kebab is covering term mostly mean special meat meal.

Döner is exist since 1800s and it is actually what you called Kebab. You know meat turning and slowly cooking vertically. It is also covering term. There are diffent meals made with döner like cağ kebabı, iskender, çökertme kebabı... And what you call Döner Kebab is just one of them Adaptation to Turkish food to German market by Turks

So what Germans call Kebab=What Turks call Döner since 1800s

And Döner invented in Turkey like any pizza is Italian food, and Döner is Turkish food.

So wrong knowledge about the meaning of Kebab not makes anything German or invented in Germany.

Döner=Turns This is what its mean by the way and cooking method.