I thought that...
Pensé que hablabas español con fluidez . I thought you spoke Spanish fluently. Thank you
4 Answers
I would use "pensaba" in this case, because you aren't referring to any specific time period. It depends on context.
Have you got a question? If you are wondering whether you should say "pensé" or "pensaba", both are correct... depending on your intended meaning.
In this context, you might rather mean,
Creía que hablabas español con fluidez.
Creí que hablabas español con fluidez.
Right!