Importing citation style to Zotero from Citavi I am a Mac user so I can't use Citavi. 
My institute has its own citation style but they only provide a Citavi citation file. I don't know a way to import a Citavi citation file into Endnote, Zotero or Mendeley so I don't have to use Windows.... 
Do you have a tip for me?
I'm sorry to say that there is no way to do that. Citavi citation styles are in their own format and there is no conversion tool.
There is a tool for Zotero/Mendeley styles that let's you find close matches that you may found useful.