Hi Kinderkids,
We want to help with your iPhone.
Are you talking about the auto-lock for when your iPhone is unlocked and turns off on its own?
This will occur due to the Attention Aware features.
If your iPhone detects that you're not looking at it, it will lock early.
You can configure Attention Aware features here:
Turn Attention Aware features on or off on your iPhone or iPad Pro
This works, even without Face ID set up.
We do recommend you set up Face ID so you don't have to enter your passcode as often as well:
Use Face ID on your iPhone or iPad Pro
It can be a security concern to enter your passcode in certain places, and using Face ID will make it so you won't have to enter your passcode as often.
Let us know if this has solved your concerns.
Thanks for using the Apple Support Communities.