Text messages have to be deleted individually. Just delete the images. Photos, videos, etc. That's what takes so much space. Tap the i in the upper right corner, then scroll down to the images. Press for delete. Check any apps you don't use much, and delete them. You can download them back later. Delete cache in apps that have that option. Others you can delete, then download back, and that deletes the cache. Delete emails that contain images. Check everywhere, like in "sent", for example. Make any music you have downloaded back to in the cloud. Local music takes a lot of space.