1.1 About backup camera: the reversing trigger wire (red thin wire) needs to be connected to the positive pole of the reversing light.
How to know which wire is the positive pole of the reversing light:
Do you have a wire tester to test the wires?
There is electricity when shifting to reverse gear;
There is no electricity when you do not shift to reverse gear.
1.2 Please check this video: https://www.tiktok.com/t/ZTL6jjdAt/

Please make sure you used the included cigarette lighter to connect. I also suggest you to use a wall plug with type-c cable to power on this unit to check if it can be turned on or not. If still not, please contact seller for a replacement.

I suggest you to try different audio output modes, you can try to use the AUX cable, FM transmission or car Bluetooth function to transfer the sound to your car speaker for louder sound quality.
Please check this video: https://www.tiktok.com/@hiehashoppe/video/7360984124011613483

4.1. Please turn off your Bluetooth and WiFi, and turn off your smartphone and turn on to try again. After you turn on your iPhone, please directly use the mirror link function. And for the mirror link, you don't need to open the Bluetooth.
4.2. If first tip didn’t help, please reset the unit back to factory mode. You can do it through - “Settings-Basic setup-Restore Factory Set-Yes”

5.1. When you set the hotspot, please pay attention to the "car"- capitalized the C in car for the hotspot will also affect it and just make sure it is in lowercase and then it will work.
5.2. Please turn off your phone and turn on to try again.
5.3. Please reset the carplay screen back to factory mode, you can do it through - “Settings-Basic setup-Restore Factory Set-Yes”.
5.4. Please uninstall the mirroring app and download it again to try.

6.1. Please use another aux cable to check if the situation improves.
6.2. If it still exists, we suggest you to add a noise isolator to the unit.