To preserve the battery, your phone will go to sleep after it is idle for a while. If you like to keep your phone screen on longer, you can change the screen timeout from display settings. Usually stock Android devices allow users to keep the device awake up to 30 minutes. If you need to keep the phone screen on longer than 30 minutes or stop it from going to sleep automatically, you can turn on the Stay awake option in the Developer options. For more details, you can refer to this guide to keep Tecno phone screen on longer. If you are using a LG mobile phone, you may have another easier option. Today, we will show you the quick steps to adjust phone screen timeout setting to make your LG phone stay on longer or even disable the auto-lock option to prevent it locking itself automatically.
Unlock your LG phone. Launch Settings. Scroll down until you find Display. Tap to open the Display screen. Scroll down to find the Screen timeout and touch to open it in a new dialog as below.

Here you can find a list of screen timeout duration, 15 sec, 30 sec, 1 min, 2 min, 5 min, 10 min, 15 min. If you choose any of the timeout duration, your phone screen turns off automatically after the selected period of time of inactivity. At the bottom of this list, you have the option to keep screen turned on until you manually turn it off. If the ‘keep screen turned on‘ option is enabled, your phone will keep its screen awake and prevent it from turning off automatically.
My phone pin lock it down and I can’t change.