Hello maherar,
Welcome to Apple Support Communities!
If we understand your post correctly, after being on a FaceTime call for an hour the screen goes blank and the pointer turns into a beach ball. We'd like to help!
A slow or busy Wi-Fi network might cause issues with your FaceTime call. If you experience connection alerts or low-quality audio or video:
- Make sure that you and your recipient have a fast Wi-Fi or cellular connection. FaceTime calls over Wi-Fi require a broadband connection.
- Check for issues that might be slowing down your connection, such as someone streaming content over your network.
- If you have questions about your Internet speed, contact your Internet service provider."
For more information check out this article: If FaceTime isn't working on your Mac
Let us know if you have any questions.
Thank you for using Apple Support Communities.
Take care!