iPhone SE 16gb Storage problems

Seems all my storage is taken up by the System. 15.8 go is being used up and my phone is literally useless. Have off loaded all my Apps except for Safari.

Have 44gb of storage in ICloud still but how make this phone workable again. I use WhatsApp Twitter and Facebook mainly and constantly delete videos and pictures after viewing but still this problem persists. Any solution to this or just have to junk phone? Can’t even download the new software update. iPhone SE 1st generation