Is there a God or this world is totally Random ?

If you are a person who believes in GOD, that's OK and if you are someone who believes in science and think concept of GOD is some fairy tale, you are right too.

So which one is it ? Should you believe in something ?

I am biased on that science side, but I would advise people to believe in some higher power. Why ?

This world is full of random events, chaos you may call it. These random events are the ones that impact your life, which can be good or bad . You can also call it Luck and some believers call it Will of God.

If you don't believe in something, you have to take full responsibility of your actions and outcomes that come of your actions. It is important to understand that the outcomes of your actions are not just because of your actions, but a combination of multitude of other peoples thinking at actions that influence the final outcome. If you only believe that the success or failure was ALL YOU, then your will get less happy as you think you worked very hard to get it and more miserable considering that you did something wrong. This can be very stressful at times. So acknowledging that there are thousands of other events, that might eventually drive the outcomes, no matter how highly you thought that outcome will be positive, but turned out to be negative that you failed. Don't blame yourself for all that. Its ALL these chaotic and random events that define our life , be it positive or negative. 

So you need to believe in randomness of life OR Luck, if you would like to call it that. You don't control it and it can just happen . You might get positive results in just one attempt or it can take ten. Sometime, you just happen to be at a place and other random events , make it the right place to be and you hit that positive outcome , OR all those random events can make it a wrong place leading to a negative outcome. You were at same place, just the random events made it the right place or wrong place, totally out of your control. 

If you are non-believer or atheist or man of science, cut yourself some slack and acknowledge that randomness plays a big role and you are not responsible for all negative or positive things happening to you. 

If you are someone who believes in GOD, continue to do that, but do evolve with the knowledge that humanity has gained in thousands of years since the scriptures were written. All the holy scriptures are observations of that time, written with the limited knowledge available. So evolve and rethink and let your GOD be guiding factor in being a good human being.