Acts 2 has a number of interesting references and I will quote each one with a little context:
1 When the day of Pentecost came, they were all together in one place. 2 Suddenly a sound like the blowing of a violent wind came from heaven and filled the whole house where they were sitting. 3 They saw what seemed to be tongues of fire that separated and came to rest on each of them. 4 All of them were filled with the Holy Spirit and began to speak in other tongues as the Spirit enabled them. 5 Now there were staying in Jerusalem God-fearing Jews from every nation under heaven.

19 I will show wonders in the heaven above and signs on the earth below, blood and fire and billows of smoke.
34 For David did not ascend to heaven, and yet he said, ? ?The Lord said to my Lord: ?Sit at my right hand 35 until I make your enemies a footstool for your feet.? ?
First, in 2:2 heaven seems to refer to the above, to the sky, to up, from God.
Second, in 2:5 it refers to the sky above; it is a trope for what happens on earth as compared with what happens above.
Third, 2:19 to me speaks of astral phenomena in the sky as an apocalyptic metaphor for political revolutions.
Fourth, v. 34 is not immediately clear but it means this: since David did not ascend (Pss 16; 110), we are to look to someone else; the One who ascended was Jesus (see Acts 1:10-11). The point being that David, after his death, did not ascend at his death. Would it be accurate to say that an OT saint ascended into heaven at death?