Dropbox app fills up entirely the local iPhone storage

Hi Jo5678, have you tried clearing the cache of the Dropbox mobile app?

Hi Jo5678, 

May I know if you enabled the Camera Uploads so the photos/videos are automatically copied on the Dropbox cloud? If the answer is yes, by default, your photos will be uploaded to a folder in your Dropbox account named Camera Uploads. You can’t change this; however, you can move your photos to a different folder in your Dropbox account after they’ve been uploaded. Once they are transferred to another folder, you may now delete the files (photos/videos) stored in your phone's photo library because the backup feature for mobile does not automatically make your photos/videos as available online only. The purpose of this is that whatever happens to your phone such as being lost/stolen, or someone messed up your photos/videos like deleted them, this will not affect what's already copied on the cloud. So if you want to use Dropbox space to free up mobile space, you need to manually delete the files in your photo gallery to make room of new ones. And don't forget to transfer the copies on another folder so that only the new copies will show in the default "camera uploads " folder by then. Hope this helps.  https://help.dropbox.com/create-upload/camera-uploads-overview