Below is how to make your iPhone more secure easily you can use.
Use a passcode or a password manager like iPassword. Go to settings > Touch ID & Passcode > Turn Passcode On and enter a six-digit code.
Disable lock screen options. Because a nefarious individual can still get into your phone via the lock screen. Go to Settings > Touch ID & Passcode > toggle the slider switch to off for Siri in the Allow Access When Locked list.
How to make your iPhone more secure easily with disabling control center
Disable Control Center on lock screen. Go to settings > Control center and toggle the slider off for Access on Lock Screen.
Turn on Find My iPhone.
You can track your lost device from another IOS device or your computer. Go to settings > iCloud > Tap on Find My iPhone and toggle the switch on for Find My iPhone.