Space not freed, space decreased, and files are all gone

Dear Box Support,

Good day.

I was organizing my files earlier. After deleting a certain amount of files, I found the space wasn't freed at all. So I checked some similar posts here and understood that it's not ok to delete the files like that and realised that I need your help.

I decided to reach out for your help later after the uploads are done. Weird thing that, at some point, I got an error message telling me that my Box storage was out of space when literally there's still above 40GB space left. 

I found it strange and checked some articles to find out why, and then logged out, cleared cookies as some articles suggested.

And after logging in just now, I found that all my files are gone, and my storage limit decreased to 10GB. 

I would really appreciate if you could please recover my files. Even better, if you could tell me why it happened, so I could be more careful to avoid all this happening.

Thank you very much.

Sincerely.