Hello Jan!
-In the first case when you had something done to you, you can say: "Me hice cortar el cabello" or "Me hice arreglar las uñas". Here you can see that the word "me" means that the action is reflexive.
-For the second case when you had something done for you, you can use: "Hice arreglar mi auto" or "Hice decorar mi casa", in these example the action is done by someone else like a mechanic or an interior designer. But if you want to say that you had something done for yourself, you can use: "Arreglé mi auto" or "Decoré mi casa".
I hope it helps.