I did a search on John 3:13 and there is a biblical question/answer site.
The writer says "Jesus was not teaching that no one had ever gone to heaven before.
Obviously, the Old Testament saints had gone to heaven (or paradise)
when they died (Mark 12:26-27), and Enoch and Elijah had been taken there without dying".
It seems that understanding Jesus is beyond the skills of many. If the Old Testament saints when to heaven when they died, then what is the meaning of John 14:6 "Jesus answered, “I am the way and the truth and the life. No one comes to the Father except through me." If OT saints went to heaven, then Jesus is/was not the Way. They didn't need him to get to the father.
When Jehovah said he is the God of Abraham, Isaac and Jacob, I am the God of the living", he wasn't stating that they are alive, but that he had the ability to give them life. as vs 24 said "you do not know the Scriptures or the power of God?" Jesus said "When the dead rise, they will neither marry nor be given in marriage" indicating future tense.