God created everything that has come into being. He is The Creator.
God created the Heaven, the creatures in heaven, the Universe, the Solar System, the Earth, the creatures on the earth.
Since He created them, He knows how they work. When human kind got deceived by the devil, we became infected with a fallen nature. Now the creation is in a state of death.
God loved us so much he wrote a book by His Holy Spirit to tell us how best to live here on the earth and who He is. We are saved by faith, but we live more healthy when we follow and obey his law (the Word).
God knows better than we do how we are to live since he is the one who created us. It is in our best interests to listen and obey Him.