the only thing that would came to my mind is when opening in Power Apps, import it the choice values into a collection and implement on "Combobox - On Change" property a remove() to remove the other values (splited by the "-" between the name and Brons, Silver, Guld") with the same starting name, if an item is within the "SelectedItems". Not sure if this would actually works, I would need to try it out tomorrow.
Maybe this idea already helps you!
Best regards Marvin
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