Dropbox added 25GB to my 2GB account without my knowledge. Now I can't access my account

I am an infrequent user of Dropbox, which is probably the issue. I admit I don't truly understand how it works.  I was put in charge of sharing photos of a memorial service on Dropbox.  Others who were sharing seem to have their own DB accounts, but everything to do with the memorial ended up on mine.

That isn't the problem.  I put all my memorial files into my DB, which resided on my disk M:.  I then moved a 25GB folder onto the same disk M, but NOT in DB.  I was careful about that.  Suddenly, that 25GB was in my DB, sending me wildly beyond the capacity my free plan allows. 

When I got the notice from DB that I had exceeded my quota, I logged onto my DB account.  It gave me options to upgrade, but no options to remove any files from DB.  

I went looking for DB on my computer and found it, on Drive M.  The 25GB folder was now in my DB.  I copied it onto another disk, then I deleted it from DB.  When I started my computer again, the 25GB folder was back into my DB.  I don't get it.  I am fully willing to admit I did something, but I have no idea what.

Judging from some things I saw in correspondence from years ago, I may have another DB account under a different email from when I used to work for a company.  I have no idea how to access this or even to find out if it is true.  My login page, after telling me that I need to upgrade does not give me any indication what account I am in.  Color me confused and frustrated.

My ambition is to move all the files out of DB and close my account(s).  I don't use it often enough to invest the seemingly large amount of hours it will take to understand it and make it work.  How do I do this?  Thank you.