I cleared all certificates from settings, lock screen. Not sure how to proceed since I can't get certificates back. I changed to a 30 min delay for lock screen but it is still inconvenient to type in every time I want to use phone.
It is possible you are confusing "Lock Screen" with "Screen Timeout".
Lock Screen will provide security to enter the phone.
The Display Timeout will turn off the Display to conserve battery. This seems to be the one to which you have chosen 30 minutes. On my phone this is the longest natural timeout for the display, though you can possibly exceed it (I have) with an automation tool like Llama or Tasker (maybe).
To disable the Lock Screen, see Settings > Security > Screen Lock, or possibly even the shorter path: Settings > Screen Lock.
Select "None" to eliminate the need for a PIN. You may have to provide the PIN one more time to accept as a credential.