Hi @Shaoan, let me see if I can help out here.
Your post has been translated to English as this is an International forum, please post any replies in English and it will be easier for me and other users to assist you. As @Strampke mentioned, you can use Google Translate if needed.
Does this regard a specific app or do you experience this behaviour from all apps and all notifications? Have you been able to check whether notifications are set to be shown or not? Find and tap Settings > Apps & notifications > Configure notifications > Show notifications.
Please get back to me with this information and I will do my best to assist you!
