My team was about to wint he game then my ps4 crashed and I received a loss and my account got banned for half an hour and I want compensation because this was a placement match
Unfortunately all disconnections and game crashes counts as leaving the match and will be penalized appropriately. The game server has no way to discern a legitimate disconnection or game crash from one that is forcefully caused by a dishonest player to bypass leaver penalties. You can learn about this policy here:
Can you be more specific with the crash? There is a known issue of PlayStation System error Ce-34878-0 commonly found in arcade game modes such as Mystery Heroes.