Hello S_w143,
Welcome to Apple Support Communities. It sounds like you're having trouble audio and video while on FaceTime calls. I'd be happy to share information that may help.
From what you've described, it sounds like it may be a network-related issue. Check out the "If you have connection or sound quality issues with FaceTime" section of this article: If you can't make a FaceTime call on your iPhone, iPad, or iPod touch.
If you're using FaceTime over Wi-Fi, check out the information here about interference: Resolve Wi-Fi and Bluetooth issues caused by wireless interference.
You may also want to test the issue in a different location, connected to a different Wi-Fi network, or by using cellular data.
Take care.