In a recent essay about school I wrote:
Ich hatte Fächer, die mir ganz gut gefallen: Deutsch, Mathe und Chemie, deren mein Lieblingsfach Deutsch ist.
It was all marked as correct other than the "deren" to which a '?' was written.
I was intending to say:
I had fun lessons: German, Maths and Chemistry of which my favourite is German.
Although this is perhaps too advanced for my level, I was intending to use a genitive plural relative pronoun. What is the correct way of saying this?