Kaltura will convert whatever format video you upload into its own format. In some cases, this may degrade the quality of the video slightly.
Kaltura will keep the original high-quality video for you to re-edit or download later, but it is still important that you keep copies of your original video material on your computer, on portable media (such as USB sticks) or in online storage (or all three).
Local computer storage
Keep a copy of your video files not only in your ACU personal drive but at home or on your laptop as well.
USB sticks may be a good portable option, and can also be used simply as a backup.
Online file storage (or "cloud" storage) can come in many forms that you have probably encountered, such as Cloudstor, Apple iCloud, Microsoft OneDrive, Google Drive, or Dropbox. Most of these services have a free space option that you can use.