I've started with Lightroom CC and CC, but my storage got full very quickly. I have the alert, but I can't access to the online storage to empty it. Online,it's written that I haven't any file on it. ...
If you sign in with your Adobe ID here: Adobe Creative Cloud you can see files you've uploaded via file sync, libraries, or mobile apps. I'd also recommend checking here in relation to this part of the storage. Deleted files go there to an "online recycle bin" which also take up space and is often overlooked.
Finally, if you use Acrobat and have uploaded files they go here Adobe Document Cloud which also counts against your storage.
Please check these and let me know if you're still facing difficulties.