God created the entire universe, including this earth. And sometimes we call everything in the sky "the sky". But it has nothing to do with "Heaven", our eternal destination.
The sky had not been prepared yet.
At the time when God created the earth, it was like a paradise. It was essentially "paradise". There was no sin. There was no death. There was no need to WORK because everything we needed was provided. Our job was simply to take advantage of it.
But then everything went wrong. And I'm talking about when Adam and Eve disobeyed God and fell into sin. And as a result, God curses this earth. Now this land has become hostile. And now, we had to work only to produce food and other things that we needed. And now, death was also a reality. And God has also created the second law of thermodynamics. Now everything was bad. Life has become a struggle.
As a result of the curse of sin, the earth was no longer a "paradise".
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If we progress in time, we learn later that God has a plan of redemption. God sent Jesus to pay the price of our sins. But this applies only to those who are willing to repent, to turn from their evil ways and to follow Jesus.
Jesus was crucified, but three days later he was raised from the dead. And after making various appearances to many people, it is about 40 days later that Jesus left this earth. And HE went "to prepare a place for us".
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If you go into the story, you can read how it all happens by reading Revelation 21 and 22.