ContentCollectionRenderer give Index to each Element

Hello everyone, the Problem i am having is the following:

I want to be able to set the index in the ContentCollectionRenderer and acces it in the other fusion (here “GalerieElement”)

grafik

I tried everything with @apply that i can think of.

I tried just asinging it with node.index or element.index which wasnt good either.

grafik

Thanks for the help in advance.