Can someone maybe help me to understand the idea behind Bitcoin, because I really don't get it.
What I understand is the idea of mining, that there is the chain where each transaction is added to and it is decentralized which means that everyone is able to run his own instance of the chain (so no government or company can controll it completely).
But lets say I own one Bitcoin (an hash). What stops me to sell this one on different chain instances? As long as I understand, they are decentralized and dont have to synchronised at each transaction. Maybe they will find out when they synchronise at one point, but then it is to late.
Also the chain become bigger and bigger as more people start to make Bitcoin transactions. At the moment the chain has just a few GB as far as I know, but in the future it will have petabytes or more...and at this point still companies like Google or governments can store it, which destroy the idea in the first place.