Why it is saying insufficient space?

El dia de hoy me aparece este mensaje en pantalla (You're almost out of space! Upgrade Now.),

quiero saber de que manera se puede solucionar este problema.

This is a warning that you are going to running out of space.

You can check it from your account link.

Please follow this screenshot:

You can delete your submissions that have file upload in it. You can take a backup of them before you delete. To backup the files, you have to manually download them by clicking the link that is seen on every form submissions.

You can also integrate your form to Dropbox next time so files can be easily accessed and organized by logging in to your Dropbox account.

If you have any further query, please let us know.