logically its sounds absurd that you challenged GOD to kill by a certain date ,since you are created by his power,he fashioned you the way HE liked ,you were not there to say that Oh GOD ! please make me smart or intelligent or make me a mutant. since you are created by him, he is in the control of your death.and he knows when to call you.
and he is not afraid of you , you should be afraid of HIM because death will come to you , and its very painful,and which will be send by GOD who lives forever!
talking about non existence of GOD , just close you eyes and think about your surrounding,about universe and question yourself who could have created this ? who is controlling everything? if you get an answer well and good else read theological books it will help!
“from ALLAH where we came, to ALLAH is our return”!
“every soul shall taste death”!
so take chill a man someday you will die , everyone will die.and if you are so much in a hurry be patient !