Can any1 explain if its theorically possible for network go down or its fully decentralized like bitcoin and have no central control?

Almost mathematically imposible. The odds are ridiculous for attackers to achieve any control over the network. I don't have the exact number but I think it was mentioned in the Elrond whitepaper in the secure proof of stake consensus part mentioning random selection of validating group.

See here for some explainations on how Elrond defend against some type of attacks: https://medium (dot) com/elrondnetwork/security-focused-q-a-a829c74caafd