Based on the information provided, it's difficult to determine the optimal play on the turn and river without knowing more about the opponent's tendencies and range. However, here are some possible lines of thought to consider:
On the turn, the opponent's bet represents a significant portion of their remaining stack, so calling puts you in a tough spot on the river if they bet again. Since you have a weak hand with no pair and no draw, you may consider folding to avoid getting into a difficult spot later.
On the river, the opponent's bet is relatively large compared to the pot size, which could indicate strength. However, the 6s on the board is a brick and doesn't complete any draws, so it's possible that the opponent is bluffing or overvaluing a weaker hand. If you believe that the opponent is capable of bluffing in this spot or betting with worse hands, you may consider calling. However, if you think that the opponent is likely to have a strong hand, you may consider folding.
In summary, it's important to consider the opponent's range, tendencies, and the board texture when making decisions in poker. Without more information, it's difficult to say for sure whether calling or folding on the turn and river is the best play in this situation.