Translation:I could talk.
i never heard somebody use "could" like this. i mean in a positive one-time past tense sentence. you can say "i could not do this last week" but in positive situation you can not. you would say "was able to" instead..
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.