Jehovah’s witnesses teach that no one goes to heaven after death. In proof of this they cite Acts 2,34 and they say that here Peter denies that David ascended into heaven and so if a man of God like David did not go to heaven it means no one go to heaven. Personally I believe David is in heaven but why did Peter say David did not go to heaven?
First, if I understand correctly, you are not exactly accurate in your description of Jehovah Witness belief about the afterlife, although you are close. I have studied their teaching fairly carefully, and if I understand correctly, they believe that 144,000 will go to “heaven,” and that the others who are forgiven by the blood of Jesus will live in an earthly kingdom here on the planet earth. So, they have two categories of those who are “saved” by Jesus–the 144,000 and all the others. Also, they teach that those who are not saved do not go to hell, but instead simply cease to exist. They are annihilated.
Having said that, your understanding of how they interpret Acts 2:34 is probably essentially correct, so let me explain that. Here, Peter quotes a prophecy of David and applies it to Jesus. Here he says, “For he did not ascend to heaven, and yet he said, “The Lord said to my Lord, ‘Sit at my right hand until I make your enemies a footstool for your feet.'” In this passage, Peter is telling us that, unlike David, Jesus was resurrected from the dead on the third day and then ascended to heaven. David neither was resurrected from the dead, nor has he ascend to heaven yet. I believe that David will be in heaven eventually, along with all those who are saved by Jesus Christ, but this passage is talking about how Jesus is unique–that he is the only one who has been resurrected and then ascended into heaven. As far as I know, there is no human who has yet been resurrected and then ascended. Lazarus was resurrected, but later died. Enoch was taken away, but never died and was not resurrected. Jesus is unique here. If the Jehovah Witnesses say this is proof that no one goes to heaven, then this is a rather obvious abuse of this scripture. I am afraid that this typical of Jehovah Witness biblical hermeneutics. They tend to read their doctrine INTO the scripture (called eisegesis) rather than taking their doctrine FROM the scripture (called exegesis).
By the way, I do NOT believe that David is now in heaven. I believe that he is in Hades, which is the biblical name for the place where people wait until the final resurrection (David would call it Sheol). Those who eventually enter heaven will rise at the end of time, be judged, and then sent to either heaven or hell. You said “I believe that David is in heaven.” I believe it is better to say that “I believe that David will be with us in heaven.”