Christians: What do you understand from these two verses in 1 Corinthians 15:44, 15:53 and how do you correlate them?

First see this 

1Co 15:50 Now this I say, brethren, that flesh and blood cannot inherit the kingdom of God; neither doth corruption inherit incorruption.

Jhn 6:63 It is the spirit that quickeneth; the flesh profiteth nothing: the words that I speak unto you, they are spirit, and they are life.

There is no flesh and blood in heaven. It is a spiritual domain.  Now your two verses should make better sense. If not then ask another question. This is important stuff. 

15:44 It is sown a natural body (we begin life as flesh humans), IT IS RAISED A SPIRITUAL BODY (our flesh bodies return to the earth in the grave - its our spirits that go before God for judgment)

15:53 For this corruptible (human flesh) must put on incorruption (spiritual life), AND THIS MORTAL (flesh) MUST PUT ON IMMORTALITY (flesh cannot live forever - only as spirits can we live forever)

Our natural body will be raised up at the sound of the last trumpet, the seventh sound. And it will be a new and improved glorified body, without the corruption of sin that is now in our body causing it to die.Our new glorified body will be beaming with the glory of God. And I believe we will be able to function and operate supernaturally in this world of the natural the same as if we were out of our natural body with only our spiritual body in the natural world.

1Co 15:44 - Here it is used to describe the bodies of earthly creatures in contrast with spiritual bodies it refers to that which is material, tangible, visible, and mortal.​

Scriptures, at 1Co 15:53, 54 and 1Ti 6:16. The basic meaning is “not subject to death.” It refers to the quality of life that is enjoyed, its endlessness and indestructibility. The anointed followers of Christ, who as mortal humans serve God faithfully, are resurrected as something more than spirit creatures having everlasting life. Jehovah gives them “indestructible life”​—an outstanding demonstration of his confidence in them.​—Heb 7:16.

This grant of immortality to the Kingdom heirs is all the more remarkable, in view of the fact that even God’s angels are shown to be mortal, despite their possessing spirit bodies, not carnal ones. So the grant of “indestructible life” (Heb 7:16) or “indissoluble life” to those Christians who gain the privilege of reigning with God’s Son in the heavenly Kingdom marvelously demonstrates God’s confidence in them.

However, whether spiritual or earthly, the individual must have a body or organism, for all persons, heavenly or earthly, possess bodies. 

In 1 Corinthians 15:50 it explains that no flesh and blood can enter God's kingdom.

And we humans are in our flesh and blood bodies on earth, so we cannot enter heaven this way.

That's why when we die, our body (which is corrupt and full of sin (Romans 7: 18 & 23) has to go into the grave to rot, and our spirit leaves our body at death and returns to God who gave it (Ecclesiastes 12:7).

However, on the day of RESURRECTION which is the last day of this earth, Jesus will return and our dead, corrupted bodies will actually RISE FROM THE GRAVE.  When that happens, we have to be changed of course, as we might be in any stage of rot imaginable - we could by then be merely dust for example so, as the Bible indicates, Paul tells us a mystery - we shall not all sleep (some of us will still be alive when Jesus returns),  but whether dead or alive when Jesus come - if we are Christians, we shall all be changed, in a moment in the twinkling of an eye at the last trump.  (We have to be changed in order to go to heaven whether we are dead or alive when He comes).

"For the trumpet will sound and the dead in Christ will be raised INCORRUPTIBLE (not dust or sin any longer).  For this corruptible (body full of sin) must put on incorruption, and this mortal (natural human being) must put on IMMORTALITY (becomes changed by God to be spiritual in the body itself).

That's why the grave LOSES IT VICTORY because it thought it had us, but in Christ we RISE and come OUT OF THE GRAVE, and that's why death no longer has any sting because we will never die again.  We are raised to live ETERNALLY with our Saviour Jesus Christ.

All of the above only applies to true born again, Spirit-filled Christians - it's not speaking of atheists or unbelievers or course, only true believers - Christians in Christ

These verses make it CLEAR that we are NOT immortal and that only believers ever become immortal for ALL of 1 Corinthians 15 is talking to those who believe in Christ. "Listen BROTHERS, I tell you a mystery..."

Vs 45 The first Adam was a corruptable body and the breath of life was breathed into him, the 2nd Adam Yeshua the Messiah was sown a natural body and raised a spiritual body by the Spirit of YHVH GOD and that is our hope. Vs 53 Our mortal, corruptible body will finally be clothed with immortality and incorruptability. Vs 55 Death where is your Victory, Death where is your sting. Paul was quoting from Isa25:8 and Hos 13:14 the prophesies given about what Messiah Yeshua would do to set us free from death and corruption, if we only trust and believe in Him and His redeeming works.

When taken in context with other scriptures it becomes VERY clear that we will inherit an imperishable spiritual body. Just was we see Yeshua was resurrected with an imperishable spiritual body.

Luke 24:36-43 As they were talking about these things, Jesus himself stood among them, and said to them, “Peace to you!” But they were startled and frightened and thought they saw a spirit. And he said to them, “Why are you troubled, and why do doubts arise in your hearts? See my hands and my feet, that it is I myself. Touch me, and see. For a spirit does not have flesh and bones as you see that I have.” And when he had said this, he showed them his hands and his feet.  And while they still disbelieved for joy and were marveling, he said to them, “Have you anything here to eat?” They gave him a piece of broiled fish, and he took it and ate before them.