You will need to put the phone in restore mode, plug it into your Mac, and restore to the latest iOS 13.6.1 release. Note you will lose any data stored on the device if you do this so backup first if you already have things on there you wish to keep.
Also if you don't have a Mac I think iTunes for Windows should do the same job. You will need a computer for the restore though.
Thanks a lot.
I don’t have anything to keep in this phone, no backup needed.
I am just concerned I might make some kind of mistake and make this phone unusable (it’s a pro max 256gb, not so cheap either).