The quality of the video you are streaming to your device and tv can be affected by many different factors. While we cannot troubleshoot individual situations, we do have a couple of tips.
Check for other devices using the internet. Is someone else streaming a movie or on a video call? Wait until they are done and try again. Each device on your network uses part of your available internet, potentially decreasing the quality of your PNB performance.
Restart your computer. We know you hear this a lot, but it can help free up space to allow your computer to run faster.
Restart your modem and wireless router. Your router works like a mini-computer, and restarting it helps end anything running that may be causing your internet to slow down.
Ask for help! Is there a tech-savvy person in your family? See if they can help you.