How do I save pictures and videos in an iPhone 7 Plus, which is showing only apple logo

The apple logo is constantly showing on the screen. It started with a “storage is full” message. Therafter I tried to delete videos and pictures, but couldn’t do it as it would reappear after deletion. I tried to buy 50 gb of iCloud storage space for limited backup, but it didn’t work, because it did not permit me to buy, stating that ‘an error has occurred’. So I decided to restart the phone, that’s since when only apple logo is continuously showing about three days now. But upon pressing together volume low button and the button on other side for about 8 to 10 seconds, it goes off intermittently and sometimes for longer duration until the phone is disturbed, eg when plugged in for charging.

I want to save videos and pics, phone is 256 gigs 7 plus. Is there any way out?