Yes, "Chef" is a false friend. On first sight I thought it was going to mean a cook in charge of a kitchen. Both English and German have borrowed it but only German has kept the French meaning.
Then... what is chef in German?
Der Chefkoch oder die Chefkoechin. Literally the "boss-cook".
So "That is my chief" is wrong, why?
it is September 2019 right now and still it is not accepted???
Why is "It is my boss" not exepted?
Because of the difference between das (this/that) and es (it)