If I understand correctly and the same description is used for multiple customers garages,, then you need to group by all the uniqueness identifiers, not just description.
I think you could just remove the joins with participations and garages, since you are not using them neither as filters nor are you getting thier fields on the select. But if you do use them, then it should do something like this.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.