Hi HerrSuur,
Thank you for using Apple Support Communities.
I see that you are having an issue with your iPhone 7 streaming videos. Videos are not playing from YouTube and Netflix. I want to help. Is your iPhone updated? If not, that would be a great first step. It’s a good idea to backup your iPhone before updating.
Here’s How to back up your iPhone, iPad, and iPod touch - Apple Support
Here’s how to: Update your iPhone, iPad, or iPod touch - Apple Support
Are your video apps updated? If not, you want to update YouTube and Netflix.
If everything is updated and the issue remains, I would recommend that you Restart your iPhone - Apple Support
Also, you can follow all the steps in this article that talks about if an app unexpectedly quits, stops responding or won’t open. These steps will also help when a Third Party App is not working properly, such as not playing videos: If an app unexpectedly quits, stops responding, or won’t open - Apple Support
I hope that helps.
Best Regards!