If you want to know what is God is, just follow the example of Jesus the Messiah.
If you understand " ...on earth as it is Heaven..." then you understand the that the Kingdom of God is/was at hand made possible by Jesus.
If you're a believer, you're a representative of the Kingdom of God or Kingdom of Heaven.
The coming fully merged Heaven and Earth, is the second coming, and Jesus will reign and rule from earth over the entire universe(s).
In short, humans create their own hell on earth by disobeying God; Jesus, through His believers are cleansing the earth of evil.
In summary, God is Jesus and the Lord is Jesus, His example is one we are to image (to be made in the image of God).