Present Perfect Subjunctive (e.g.: tú hayas hablado)

Questions about the past perfect subjunctive

Q:  Why is it Quiero que tú hayas dicho and NOT Quiero que tú has dicho or Quiero que tú habías dicho?

The verb querer, here in the present, requires the use of the subjunctive in the subordinate clause, NOT the present or past indicative. Review and memorize the triggers for the subjunctive.

Q: Why is it ... después que lo ha hecho and NOT ... después que lo haya hecho?

The expression después que is followed by the indicative, while antes que is followed by the subjunctive. This makes sense because we can be more certain about events after they happen than before. With después que, it is implied the event occurred, so the indicative is required.

Q: Why is it creo que ha venido and NOT creo que hayas venido?

The verb creer is followed by the indicative in affirmative (positive) sentences, but followed by the subjunctive in negative ones (the idea being that there is less certainty in the latter case), e.g.: No creo que hayas venido.

 Q: Why is it nopienso que lo haya sabido and NOT no pienso que lo ha sabido?

The verb pensar is followed by the subjunctive in negative sentences and by the indicative in affirmative (positive) sentences (the idea being that there is certainty/assertion, rather than doubt, in the positive case), e.g.: Pienso que lo ha sabido.