Key Noir Themes
Alienation: The main character is usually alone in world of crime and corruption. He's usually the most moral out of all the main characters and ends up feeling alone as a result.
Corruption: From the beginning, in the middle, and at the end, there is a ridiculous amount of corruption surrounding the main character, in both the world he lives in and the people around him.
Feminine Betrayal: Whether it's a man being effeminate - and therefore "weak" - or a woman destroying his life, either on purpose or by accident, men in noir stories are often drastically hurt by the introduction of a woman. This also brings up the themes of sex and lust, which are seen as both unavoidable and damaging.
You can find elements of these themes in past works you've read and worked on in school such as:
J.D. Salinger's Catcher in the Rye (alienation)
George Orwell's 1984 (corruption)
Aldous Huxley's Brave New World (corruption)
Albert Camus' The Stranger (corruption and alienation)
All of these books can give you new perspectives on the noir themes here and strengthen the core of your writing.