It is sad and frustrating. The update makes my phone heats up quicker than it should have. I am sorry I wish I could offer you a solution to this. I have wiped my phone and it is worse, sad to say I have lost half of my data to a bad security update
So sorry to hear you have lost half your data, this shouldn't be happening plus the phone heating up, that's a concern too. When you contact Samsung they don't help with the issue if I'm honest. Just talk you through the usual jargon which never resolves it! I really hope this gets sorted for those of us that have been effected.