Same temperature monitoring system through HABEROCEAN mobile App can be seen on my latest post https://haberocean.com/2020/04/real-time-temperature-monitoring-and-device-control-from-mobile-app-developed-on-flutter-through-nodemcu/. App screenshots are shown in the following image.
Upload the following program to your NodeMCU. It is a direct communication between your mobile device and NodeMCU. So, after uploading the program, search for available WiFi devices on your Android device. In the available WiFi devices, you could see a device named Cooling-Fan-Controller.