Is Quantum World weird?
Yes, Quantum physics is weird. Once you get into Quantum world one thing you will realize rapidly that the smaller the thing the weirder it is and the laws of Quantum world are so strange that if you follow them to their logical conclusion you will realize that it's only getting strange. That's why Quantum physics is full of Thought experiments.
So What is Quantum Suicide?
Quantum suicide is a thought experiment originally published independently by Hans Moravec in 1987 and Bruno Marchal in 1988, Then it was further developed by Max Tegmark in 1998. So imagine a gun that is hooked into a machine that measures the spin of quantum particle everytime the trigger is pulled if the particle is spinning clockwise the gun will fire if the particle is spinning anti-clockwise the gun won't fire so chances are 50% that the gun will fire and the gun won't fire. Now everything is ready now its time to shoot someone but before shooting someone you shot some random objects and you made 7/10 successful shots now you are taking it to the next level you are going to Shoot someone his name is John however on the third attempt the gun fired and John died since its all random now you have pointed the gun to your head and pulled the trigger tick, tick, tick, tick the gun didn't even fire it means 0/10 successful shots but why here is the reason in the light of quantum suicide. According to quantum suicide, every time you pulled the trigger the timeline splits into two timelines. In one timeline you are alive and in one you are dead and because your consciousness only continued in the universes in which the gun didn't fire, that's why you survived all the gunshots.
So, Are you Immortal now?
Well, No this doesn't make you immortal because even if you do a quantum suicide and go to other universes and continue your consciousness you will eventually die by aging or accident or any disease.
Thought Experiment, Hmm
Quantum suicide is a thought experiment that can't be proved by science even if someone tries it and became successful no one will believe you. To prove it to everyone you'll have to blow up the whole earth with a quantum bomb with 50% chances of dying and surviving.
So, What happened to john?
Well, John should be alive in other timelines but in your timeline he is dead and here you will have to go to jail.