Hey there Jefersonsaldanha,
Thanks for reaching out to the Apple Support Communities. We understand you're having issues when watching movies on Netflix, and we'd be happy to provide you with the best options.
To get started, are you only experiencing this issue with the Netflix app, or have you noticed issues with stuttering when watching movies/videos in other apps as well? If this is only occurring in the Netflix app, take a look at the steps listed in the following resource that may help: If an app on your iPhone or iPad stops responding, closes unexpectedly, or won’t open - Apple Support
We understand you're not having issues with the app closing unexpectedly or not responding; however, the steps listed in the resource above can help with troubleshooting other issues as well.
If still having issues after going through the steps above, and if this is only occurring on the Netflix app, the next best option would be to reach out to the app developers for additional assistance.
For help with reaching out to the app developers, take a look at this link here: How to contact an app developer - Apple Support
We hope that's able to help.
Take care.