5D cannot be understood with the limited mind, though 5D can be felt through Consciousness. The mind is restricted to 4D, it cannot go beyond because the mind itself is a 4D entity. You also cannot have a memory of 5D, since memories are 4D constructs as well. You may have a memory of a transcendent experience, but the actual 5D connection is only truly felt in this Present Moment. Any memory you have is just a pale reflection.
There’s a whole lot of people and channelers who get the upper astral (part of 4D) confused with the Celestial Realm (5D). The upper astral contains the religious “heavens”, created largely out of what people believe they’re supposed to see, and it contains things like the Akashic records. If it resembles the physical realm at all, if it’s not a totally ego-eradicating, mind-blowing feeling of transcendental bliss, it’s not 5D.