iPhone X storage issue....too many videos...

HELP!!! I have an iPhone X and don't really want to pay the money for a new iPhone right now. I am to the point where I cannot have more than the basic apps open (I've offloaded or deleted the others). I am almost positive that my storage is overly consumed with photos and videos and large attachments to messages. I've tried uploading photos to Amazon Prime, an external USB device, my HP laptop and the iCloud but am not very tech savvy. My original idea I keep coming back to is to make sure each "large attachment" is backed up by the actual video and then deleting the "attachment". But now, when I go back to a text string and tap on the name of the group none of the pictures or videos show up at the bottom of the description of the group. I've tried turning the phone off and on. Any suggestions? I'd be greatly appreciative.