Hey there ximena172,
We understand you're experiencing an issue with the video quality when watching movies on your Apple TV.
Check out this resource: If you can't watch or stream movies and TV shows in the Apple TV app
Specifically, the section below may help:
"If the video quality is bad or it stops playing
- If multiple people on your network are using the internet, your connection speed might slow down. Ask them to temporarily pause their internet activities.
- Restart your Apple TV, iPhone, iPad, iPod touch, or Mac. If you're using a smart TV or streaming device, turn it off and back on again.
- Tap or click the download icon to try downloading the movie or TV show instead.*
* You can't download movies or TV shows to Apple TV, smart TVs, or streaming devices. You can only download HDR content on certain iPhone, iPad, and iPod touch models, and you can't download 4K video content to any device."
Regards.