opt for profile whose video quality parameters you want to change.
tap the button next to the video quality you want to use on all of your devices and clickSave.
That’s because Netflix charges extra for its 4K plan.

to make it get 4K video, you’ll need to upgrade to a plan which includes that option.
From theAccountscreen, clickChange Planand selecta 4K option.
How Do I Change Video Quality in the Netflix App?

In theVideo Playbacksection, tapCellular Data Usage.
Your options are:
Make your choice and tapXto return to the app.
to get to select anything other thanAutomatic, you have to firstdeselectit.

Then, you’re free to chooseSave Data, for example.
After choosing a different option, you have to pressOK.
Netflix detects your available bandwidth and automatically adjust video quality to match it and to deliver video to you.

That generally works pretty well and is the best you’re free to do.
Changing the video quality won’t help when Netflix is buffering.
Online games, downloads, and people streaming in other rooms can all slow down your connection to Netflix.

Turn off anything that might be using up bandwidth.
Otherwise, trytroubleshooting your internet connection.