Screen Lock

1. Open Settings.
2. Tap "Display & Brightness."
3. Tap "Auto-Lock."
4. Choose the amount of time you want your screen to stay on after you last touch your iPhone. Your options are 30 Seconds, anywhere from one to five minutes, and Never.

Hi,

Hope this helps - https://www.businessinsider.com/how-to-keep-iphone-screen-on?r=US&IR=T