I want to say that my key is hanged on hanger. How do I say that?
1) My key is hanging on hanger
OR...
2) My key is hanged on hanger
My key is hanging on a/the keyhook.
A "hanger" in BrE is the plastic or metal thing that you hang your clothes on in the wardrobe. They're officially called "clothes hangers" but most people just refer to them as hangers.
The small hooks you hang keys on are keyhooks.
Note that whatever noun you use for the hook, you need to add the article before it.
Remember to capitalise the word "I" (first person singular) at all times.