Translation:I could talk.
Agreed. "I could talk" in this form is a conditional offer (or threat) to talk. I would be able to talk. I have a lot to say; I could talk if I wanted to. It is definitely not in the past. For the past we have to say "I was able to talk". Now, when it is in context, or is a part of a larger structure in the past, it can become a past tense statement. "When I was a little child, I could talk for hours". But just by itself it's not a correct translation of "Konuşabildim". In my opinion.