Another question, how can i use a private gitlab repository when fetching e.g. kustomization files?

this isn't supported rght now, I don't think. they need to be accessible via http, without a password

hmm, but you can create a gitlab provider with some oauth token, its not possible to use it to download some resource ?

the gitlab provider just cals the gitlab api. the kustomization support uses a http fetch mechanism to download files locally and apply them to a cluster, theyre quite different

ok thanks for clarifying