iPhone XS Max 256gb memory full error 14

I’ve got a serious problem with my iPhone XS Max 256 Gb

It started when my phone memory was full and it was working too slowly. I tried to do iTunes backup but it failed. I tried deleting some apps and videos, but to my surprise, I was not able to do it. I rebooted it, and it got stuck in a boot loop (apple logo). I then tried to put in in Recovery Mode and update it via Mac/PC (It did not have the latest iOS). The upgrade failed halfway through with Error 14. Now it is stuck in Recovery Mode.

I've read a lot of messages from people who have the same problem! We need a skeleton IOS for this situation! Apple have really made a mistake in allowing a phone to reach such a full capacity.

Support service recommended me to restore my phone with no opportunity to save my data! That’s completely impossible! My photos and videos were an integral part of my life. There should be the way out! Help me, please!