My professor said that the addition of fluorine renders fluorinated steroids unable to be broken down by the liver. t or f?

Variable.: Fluorination of some molecules, including steroids, can block metabolism by liver enzymes in some cases, depending on the molecule, and where the fluorine atom is attached on that molecule. But most fluorinated steroids are applied topically; unless they are grossly over-used, not enough of the drug is absorbed into the bloodstream to make this a relevant issue in the real world.