How to back up when a system UI error occurs.

Hi.

When I turn on the phone, after entering the password pattern, the LG logo will appear on the screen but the system will not go up.

And this message appears on the screen:

Unfortunately the system UI has been stopped.

I have important information on the phone's internal storage, which I have not unfortunately backed up.

I tried to back up the phone using some software on my computer.

But the computer does not detect the phone.

It seems that you need to enable usb debugging.

How do I back up my phone information?

Files on my phone are more important to me than repairing my phone.

I'm looking for a way to back up phone files.

Or if I'm not able to back up, I'm looking for a way to recover files after the phone reset or flash.

Please guide me if anyone can.

Thanks everyone.