How do I reset my account

I would like to completely reset my account, as there is a huge percentage of cloud space used by I don't know what data. If it wasn't possible would I at least be able to completely delete from my account my free document cloud plan?

I tried doing so by issuing an account deletion request, only to discover that wouldn't have freed up my email address (btw, that should be stated before deleting the account).
I'm not a lawyer but that made me wonder also about the legal conformity of this practice with GDPR. Wasn't a company supposed to completely delete my data in the case I requested its deletion? That didn't happen at all here.

Thanks in advance.