2 Corinthians 12:1-3
King James Version
12 It is not expedient for me doubtless to glory. I will come to visions and revelations of the Lord.
2 I knew a man in Christ above fourteen years ago, (whether in the body, I cannot tell; or whether out of the body, I cannot tell: God knoweth;) such an one caught up to the third heaven.
3 And I knew such a man, (whether in the body, or out of the body, I cannot tell: God knoweth;)
2 Corinthians 12:1-4
A Special Blessing in Paul’s Life
12 There is more that I have to say about myself. It won’t help, but I will talk now about visions and revelations from the Lord. 2 I know a man in Christ who was taken up to the third heaven. This happened 14 years ago. I don’t know if the man was in his body or out of his body, but God knows. 3-4 And I know that this man was taken up to paradise. I don’t know if he was in his body or away from his body, but he heard things that he is not able to explain. He heard things that no one is allowed to tell.
This is the passage you are referring to and asking the question of dimensions/portals if they are real? In truth this concept will be much easier to acknowledge by knowing that the Bible are stories made up by God simply as writings of literature. This sounds like a speculation placed in the Bible for an explanation in the final days or like a plant used to be explained later.
First off, the Bible clearly says it was a dream or vision given to another man that the character apostle Paul knew 14 years ago. The man that told of his dream, if he experienced being actually in a special place mentally or not Paul did not know. This is a story about dreams and how they can affect people. This is the same as in Revelation where the apostle John says by inspiration he was in “The Lord’s Day”, Revelation 1:10. Strong mental situations that happened to people as we are aware that the Bible are simply stories made up. This is a story told about a man that went to sleep and when he awakens, he told people his feelings and information he recalled about his dream.