Yes i believe that god exist because he created us, all living and non living things. And everythings happen it is the will of god. He will not give a thing or anything that will harm you.
What about brain cancer?
What? Do you think brain cancer exists because it "created us, all living and non living things? And everythings happen it is the will of" brain cancer?
You gotta have a few screws loose.
He said God would not cause anything that will harm us, and yet God, being all-knowing and all-loving, created a world in which bone cancer exists, he created insects that burrow into the eyes of children and make them blind, he created diseases like proteus syndrome and Fibrodysplasia ossificans progressiva. Even if you argue he did not create these directly, but are the result of evolution or the work of Satan, God, being all-knowing, still allowed them to exist, and hence through his inaction is responsible for their continued existence.
God is a maniac.
You are not taking into account several things. Among them are freedom, God-likeness, and your decision to be against God.
In general, people were made in God's likeness - God's image. This includes freedom. We don't know if Satan was made with this God-likeness. But we DO know that he has power from God.
We are the ones who let Satan in, through Adam and Eve listening to Satan, and eating the fruit. We are the ones who maintain Satan in our lives by fighting against God, if only by thinking that He is at least slightly evil, or a maniac.
We are like embryo Gods. We can do nothing without God. Yet because of Who He is - all love and all giving - He has to give us what we ask for if He wants to remain the loving, giving God He is. So, when we listen to Satan by asking for bad stuff, God gives it. But He realizes that we are asking from a standpoint of stupidity and inexperience. So He gives us a way out at the same time.
The way out is Jesus salvation. The way out of the badness and the trouble is the future life that will happen to us after we die out of this life.
Yet, God hasn't stopped giving us what we ask for in THIS life. If we ask for eternal death by asking to be against God and His salvation in Jesus, He will give it to us.
The problem isn't God. God gave us the best... to be like He is. The problem is how we use our God-likeness... to accept God and His Jesus salvation, or to destroy ourselves.