Is God in control of this world or is Satan?

That is a difficult question because the Bible claims that both are in control.

Let everyone be subject to the governing authorities, for there is no authority except that which God has established. The authorities that exist have been established by God.

Romans 13:1

We know that we are children of God and that the whole world is under control of the evil one.

1 John 5:19

Satan and his demons possess enormous influence over the world and even over the circumstances of Christians, yet Satan never has God’s approval but does nothing without God’s permission. When Satan carries out his evil strategy, it is only because God has a good reason for allowing him to do so. God is all knowing all powerful; he is almighty God and his ways are beyond our understanding.

While it’s easy to blame Satan for all of the worlds’ problems, many times it is our own sinfulness that is the cause. Speeding and driving recklessly, losing control and hitting a tree. That was not Satan but you being stupid.