Hi Pashalitsa,
Thank you for posting here in Apple Support Communities. We understand that all of your photos and videos have gone missing from your iPhone. We know how important photos and videos are, so we'll definitely help get you on the right path for a possible resolution. To start, we'd just like to ask you a few question, and have you check out a few things.
Did this happen during the actual backing up process, or were you restoring your iPhone from a backup?
Would you be OK with checking to see if there are any other backups of your iPhone? Here's how: Locate backups of your iPhone, iPad, or iPod touch
Aside from backing up your iPhone, do you also import photos from your iPhone to a computer? Transfer photos and videos from your iPhone, iPad, or iPod touch
Have a look at this resource to see if it can help you locate photos: Get help with missing photos
We look forward to hearing back from you.
Cheers!