Why do all the previous messages disappear after my mobile phone is set with privacy space?

That's true. I've met it before. I suggest that you often back up your personal data, such as call records, SMS records, contact information updates, etc ... download a Q synchronization assistant and come down when necessary. Simple and convenient. I've been using it. I recommend it to you! I hope it will help you, and don't be angry, don't be angry!