why i am unable to set screen timeout duration

[Android Central Question]

Phone: Huawei y5 prime 2018
Android Version: 8.1.0
I want to extend the time it takes for my phone screen to sleep but when I go to Settings --> Display --> Sleep, the sleep button is grayed out and I can't change the setting. It is stuck on 30 seconds.

 

[belodion]

Any battery-saving set?