"Sen bana cevap vermedin." Translation: You did not answer me.
You did not give me an answer.
Vermek (verb) "to give."
"Vermedin" --> you did not (give)
Hey! Duo dinged me for writing "You haven't given me an answer"! What's up with that???
I cannot explain your declined answer.
"Have not" has a negation aspect to it --> "değil"